Before the start of business, Just Security provides a curated summary of up-to-the-minute developments at home and abroad. Here’s today’s news.

IRAN NUCLEAR TALKS

A group of 47 Republican senators wrote an open letter to Iran’s leaders, warning them that any agreement concluded with the Obama administration could be revoked by the next president “with the stroke of a pen” and “future Congresses could modify the terms of the agreement at any time.” The letter, authored by freshman Senator Tom Cotton, was signed by Majority Leader Mitch McConnell and a number of potential 2016 presidential candidates. [Bloomberg View’s Josh Rogin]

The GOP letter deepens the battle with the White House over the Iran negotiations. President Obama said “it’s somewhat ironic to see some members of Congress wanting to make common cause with the hardliners in Iran,” in response to the letter. [Washington Post’s Greg Jaffe and Sean Sullivan]  Vice President Joe Biden sharply criticized the Senate Republicans in a lengthy statement, stating that their letter “sends a highly misleading signal to friend and foe alike that that our Commander-in-Chief cannot deliver on America’s commitments—a message that is as false as it is dangerous.” [Huffington Post’s Igor Bobic]

The Iranian foreign minister dismissed the letter as a “propaganda ploy.” In his statement, Javad Zarif said:

“I wish to enlighten the authors that if the next administration revokes any agreement with the stroke of a pen, as they boast, it will have simply committed a blatant violation of international law.”

Democrats criticized the letter for interfering with international negotiations, with Senate Democratic Leader Harry Reid accusing the signatories of “empowering the ayatollahs.” [The Hill’s David McCabe]

Seven Republican senators refrained from signing the letter amid concerns that it could undermine the GOP strategy on a nuclear deal. Senate Foreign Relations Committee chair Bob Corker said the letter could detract from his ultimate goal of obtaining a veto-proof majority for a bill that would require congressional approval for an Iran deal. [Politico’s Burgess Everett and Michael Crowley]

Republicans are “crossing a dangerous new line” by seeking to undermine U.S. foreign policy, explains Max Fisher at Vox.  The GOP letter “undoubtedly” offers Iranian hardliners “another argument to use in opposing an agreement,” argues Carol Giacomo at the New York Times.  And the Wall Street Journal’s Gerald F. Seib explores whether Congress could “blow up” international talks conducted by a U.S. president and involving all major global powers.

[Later this morning, Robert Howse and Ruti Teitel will have a post at Just Security on the “Legal Flaws in the 47 Senators’ Letter to Iran.”]

The International Atomic Energy Agency expects further information shortly from Iran, a senior agency official has said. Iran is at least six months behind in offering technical information to the IAEA in its talks that are running alongside the negotiations with the P5+1. [Reuters’ Shadia Nasralla]

The “central question” that Iran has so far been able to avoid is whether it has the knowledge to build an atom bomb. William J Broad and David E. Sanger report on the issues that Iran has declined to give technical answers to the International Atomic Energy Agency. [New York Times]

IRAQ and SYRIA

The battle for Tikrit. Iraqi military and Shi’ite militia groups claimed the center of a town on the northern edge of Tikrit from Islamic State fighters today, closing in on Saddam Hussein’s home city, reports Reuters.

Iraqi Kurdish peshmerga fighters have launched an offensive against ISIS militants in Kirkuk province. The fighters, backed by U.S. airstrikes, began advancing along a frontline south-west of the provincial capital yesterday. [BBC]

Almost 100 captives have escaped an ISIS-run prison in the north of Syria, including about 30 Kurdish fighters, according to the Syrian Observatory for Human Rights. [Reuters]

The U.S.-led coalition would “consider” intervening to prevent the group’s destruction of antiquities, according to Gen. Martin Dempsey, although the U.S.’s top military officer stopped far short of promising action. [Washington Post’s Adam Taylor]

A 19-year old German woman has become the first western female fighting against the Islamic State in Syria to die during battle. [Deutsche Welle]

U.S.-led airstrikes continue. The U.S. and coalition military forces carried out five airstrikes against Islamic State targets in Syria on March 8. Separately, the U.S. and coalition forces carried out a further nine strikes in Iraq. [Central Command]

The Islamic State has launched its own version of Facebook, as the group faces a ban from mainstream online social media networks. The ‘caliphate book’ reportedly got off to a “bumpy start” as it was offline yesterday, just one day after its launch. [Reuters]

ISIS is extending its reach worldwide, with Boko Haram’s reported allegiance pledge only the beginning. Nancy A. Youssef reports on the Islamic State’s model which is likely to involve resources and training being offered to the Nigerian group to “create a distinct province.” [The Daily Beast]

Cracks in the Islamic State are becoming apparent as the group expands, with reports that it is struggling to maintain unity as corruption, ideological differences, and defections begin to rise, writes Maria Abi-Habib. [Wall Street Journal]

The death last week of Canadian soldier Sgt. Andrew J. Doiron has prompted frustrations due to discrepancies between the Canadian and Kurdish accounts of his death. Dan Lamothe offers further details. [Washington Post]

Tim Arango and Eric Schmitt explore the situation surrounding Turkey’s porous border into Syria, which despite pressure from western allies to tighten the border, continues to facilitate the flow of fighters across the frontier. [New York Times]

The U.S. is being sued by plaintiffs on behalf of Iraqis who worked alongside Americans during the war in Iraq, on the basis that the years of delay in processing visas for entry to America endangers their safety. [Wall Street Journal’s Miriam Jordan]

UKRAINE and RUSSIA

Pro-Russian rebels have withdrawn a “significant” amount of heavy weaponry from the front lines, Ukrainian President Petro Poroshenko has confirmed. [BBC]  Poroshenko said that 64 soldiers have been killed in eastern Ukraine since the ceasefire took effect last month. [AFP]

Russian President Vladimir Putin has publicly indicated that the plan to annex Crimea began weeks before the March 2014 referendum, which the president had consistently cited as the reason for annexation. [New York Times’ Neil MacFarquhar]

SURVEILLANCE, PRIVACY, and TECHNOLOGY

The U.S. has filed its Second Circuit brief in its dispute with Microsoft regarding the reach of the government’s warrant authority under the Electronic Communications Privacy Act. Check out Jennifer Daskal’s analysis of the brief at Just Security.

New Zealand Prime Minister John Key has retracted a 2013 promise to resign if mass surveillance by the country’s intelligence agency, the GCSB, was proven. [The Intercept’s Glenn Greenwald]

Wikipedia will file a lawsuit against the NSA and the Department of Justice, challenging the legality of the government’s mass surveillance program. [Reuters]

U.S. air traffic control may be vulnerable to hackers, according to a Government Accountability Office report released last week. Sen. Charles Schumer has demanded “immediate action” in light of the report due to concerns that a plane disaster could be caused by a Sony-style hack. [New York Post’s Khristina Narizhnaya and Sophia Rosenbaum]

HILLARY CLINTON’S PRIVATE EMAILS

Hillary Clinton will likely address the controversy surrounding her use of private email at a press conference in New York in the coming days. [Politico’s Glenn Thrush and Josh Gerstein]  In a press briefing yesterday, press secretary Josh Earnest acknowledged that President Obama corresponded with Hillary Clinton via her private email address while she was secretary of state. [Politico’s Kendall Breitman]

The Washington Post editorial board calls on Clinton to give forthcoming answers about her decision to use a private email, rather than “stonewalling” the public.

OTHER DEVELOPMENTS

The U.S. has declared Venezuela a national security threat. President Obama signed and issued an executive order yesterday placing seven Venezuelans under sanctions, but did not target the country’s energy sector or wider economy. The White House said the order was targeted at those who violate human rights of Venezuelan citizens or are involved in public corruption, but Venezuelan President Nicolas Maduro denounced the move as an attempt to defeat his government. [Reuters’ Jeff Mason and Roberta Rampton; White House]

The Islamic State’s Libyan affiliate abducted nine foreigners and beheaded eight Libyan guards in an attack last week on a central oilfield, officials said yesterday. The incident was part of a string of deadly attacks on the Libyan oil infrastructure by ISIS. [AP]

Forces from Chad and Niger have reclaimed two northeastern Nigerian towns from Boko Haram as part of a joint offensive that has left around 200 militants and 10 Chadian soldiers dead, according to a Chadian security source. [Al Jazeera]

A suicide attack in Egypt’s Sinai Peninsula has killed a civilian and wounded 25 Egyptian police officers, according to security forces. The attack is the latest in a series of attacks in the region; a roadside bomb killed three Egyptian soldiers in Sinai on Monday. [Al Jazeera]

The International Criminal Court asked the UN Security Council to take “necessary measures” to enforce Sudan’s compliance following the country’s ongoing refusal to extradite its leader for trial on charges of genocide in the Darfur conflict. [New York Times’ Rick Gladstone]

Gulf states have agreed to host Yemen peace talks in Riyadh, Saudi Arabia, in an effort to end the crisis in the country. [Al Jazeera]

U.S. naval hegemony is “secured by such a dramatic margin that no naval buildup is needed;” Gregg Easterbrook makes the case against naval expansion. [New York Times]

Pakistan’s war on terror is resulting in the deaths of hundreds each year in Karachi, and claims of police extrajudicial killings in the city have sparked outcry, report Nathan Hodge and Syed Shoaib Hasan. [Wall Street Journal]

U.S. ambassador to the UN Samantha Power called on European states to provide more peacekeepers to UN missions, noting their numbers have dropped steadily since the massacre in Srebrenica. Power said President Obama will host a summit in September to push for greater personnel commitments. [Wall Street Journal’s Laurence Norman]

Yesterday marked the eight year anniversary of the disappearance of former FBI agent Robert A. Levinson after he travelled to Iran in 2007. The FBI has increased the reward up to $5 million for information that leads to his location and safe return.

The UN special rapporteur on human rights in North Korea called for the state to account for the suspected abduction of hundreds of foreign citizens over a number of decades. [New York Times’ Nick Cumming-Bruce]

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