President Donald Trump’s attendance at the NATO summit in Brussels this week was defined by a combination of antagonism and spectacle, leaving allies alienated and confused. After lobbing insults at Germany and lecturing allies on their levels of defense spending, Trump closed out the summit dedicated to European security, by casting doubt about his position on key issues such as Crimea’s status and whether the U.S. would continue military exercises in the Baltics.

Leaving the alliance more divided and uncertain than it has been in its 70-year history, Trump now heads to a bilateral meeting in Helsinki on Monday with Russian President Vladimir Putin. The agenda is expected to cover a series of controversial issues including Syria, Ukraine, and Russia’s election meddling. However, there is one issue that should be a red flag if it’s at all a part of the discussion: sanctions relief for Russia.

Should sanctions relief, under any circumstances, be part of an agreement reached in Helsinki, Congress will need to step up and fulfill its oversight responsibilities. This starts by holding immediate hearings of inquiry and asking some very difficult questions.

Sanctions repeal for Russia has been a priority for Trump from the very beginning of his administration. Even as early as the transition, National Security Advisor-designate Michael Flynn famously spoke to Russian Ambassador Sergey Kislyak five times in one day about the Russian response to new Obama administration sanctions. Conversations he would later lie to the FBI about. And one of the very first agenda items the White House pursued in early 2017 was to try to roll back sanctions levied against Russia under the Obama administration. This effort failed thanks to strong pushback from career national security officials and intervention from Capitol Hill.

Eventually, Congress felt the need to codify these sanctions into law and, in July 2017, drafted the Countering America’s Adversaries Through Sanctions Act (CAATSA). Despite the White House’s aggressive lobbying against it, the legislation eventually passed with a nearly unanimous vote in both chambers of Congress. Facing a veto-proof majority in Congress, Trump was forced to sign the bill in August 2017, but accompanied it with a signing statement opposing the legislation, calling it “seriously flawed” and suggesting parts of it were unconstitutional because it “encroaches on the executive branch’s authority to negotiate.” The Trump administration has since bungled implementation of the law by fulfilling some requirements in a way that actively undermined their intended purpose, while just ignoring others.

Trump has even made Putin’s case to the world telling an international audience in November 2017 that, “People don’t realize Russia has been very, very heavily sanctioned…. And I feel that having Russia in a friendly posture, as opposed to always fighting with them, is an asset to the world and an asset to our country, not a liability.”

Trump’s views on this issue are clear.

But there is zero policy rationale for any sanctions relief absent a dramatic and unrealistic shift in Russia’s stance on key issues. The purpose of sanctions is not to punish Russia or even the targeted individuals. The intention is to influence decision-making and behavior coming out of the Kremlin.

There are three categories of malign behavior from Moscow that the current sanctions regime has been put in place to respond to: 1) Russia’s illegal actions in Ukraine beginning in 2014; 2) its human rights abuses at home; and 3) its interference in western democracies, especially the 2016 American election.

In each of these cases – Ukraine, human rights, and election meddling – Russia has done nothing to alter its behavior. Russia continues to occupy Crimea and engage in “a low-intensity but still very real war” in Eastern Ukraine, which has claimed 10,000 lives so far. The crackdown on Putin’s political opposition remains rampant, as does the persecution of LGTBQ community members in Chechnya. Meanwhile, Dan Coats, the director of National Intelligence appointed by Trump, has been warning that Russia’s election interference is ongoing and that it’s targeting the 2018 midterms.

Given this, it’s disconcerting that a delegation of congressional Republicans was in Moscow last week – during the July 4 holiday – calling for stronger ties between the U.S. and Russia, and reportedly there to observe the effect of western sanctions on the Russian economy. Absent from the trip were any Democrats. This is an unusual step for a congressional delegation, but particularly inappropriate given that the U.S. intelligence community assessed – and just last week the Republican-led Senate Intelligence Committee confirmed – that Russia interfered in our election to assist Trump win.

Also absent from the trip were any of the traditional foreign policy voices. In fact, with the exception of Rep. Kay Granger (R-Texas), none of the delegation’s members sit on any relevant committees. Contrast this with another congressional delegation in the region at the same time, which included a bipartisan group of senators from the Foreign Relations Committee, led by the committee’s chairman, Sen. Bob Corker (R-Tenn.). The message on their trip was very different: They expressed their commitment to the transatlantic alliance between Europe and the U.S. and support for strengthening Baltic security.

So, why did this GOP delegation go to Moscow?

If the answer is that they were there as part of an effort to explore sanctions relief ahead of Trump’s summit with Putin, then this should be an important warning signal for congressional leadership and the relevant committees in Congress.

This is not to say that any deal that comes out of the summit should be opposed outright. Diplomacy is important, and one could imagine a dream scenario where sanctions rollback would be part of a broader agreement reached between the two leaders. For example, sanctions relief would be welcomed if it were part of a deal where Putin agreed to implement the Minsk II agreement and return Crimea to Ukraine; to come clean about its election meddling and put in place a verifiable means to ensure no further interference in other countries’ democratic elections; to ease its political repression at home; and to discontinue its violations of the Intermediate-Range Nuclear Forces (INF) Treaty while agreeing to an established framework for a New START extension to further reduce each country’s nuclear arsenals.

If such an agreement were reached, with real and verifiable metrics and detailed plans for implementation, it would be the crowning foreign policy achievement of the Trump administration – and a real accomplishment. But the reality is that such a deal is not only unlikely, it doesn’t appear to be desired by the president.

Given the president’s history of advocating for sanctions repeal, and the fact that he and his campaign are currently under investigation for potentially conspiring with Russia, any “deal” reached next week should be viewed with extreme skepticism. And if there is an agreement out of the Putin-Trump summit that includes sanctions relief, Congress must act and act immediately.