The U.S. House of Representatives is expected to pass a bill on Tuesday which will make it harder for President Donald Trump to ease sanctions on Russia without approval from Congress.

The bill comes after a rare show of unity between congressional Republicans and Democrats and signifies another blow to Trump’s hopes for a rapprochement with Russia.

Here’s why Tuesday’s vote matters:

The bill comes after a bipartisan group of House and Senate negotiators reached an agreement on Saturday pledging more sanctions on Russia.

The sanctions are aimed at punishing the country for alleged meddling in the U.S. presidential election, its annexation of Ukraine in 2014 and military involvement in Syria.

In June, the Senate passed legislation that would impose additional sanctions against Russia and restricting the power of the president to lift them. But what was more surprising was the unity shown between both Republicans and Democrats this weekend in support of the legislation.

The bill, which also includes new penalties against North Korea and Iran, would require the president to submit to Congress a report on proposed actions that would “significantly alter” U.S. foreign policy towards Russia, including any bid to ease sanctions.

Congress would have at least 30 days to hold hearings and then vote to uphold or reject Trump’s proposed changes, Reuters reported. Trump could potentially attempt to veto the bill but this would risk a backlash from both Democrats and his own party, it also risks the humiliating possibility of Congress overturning his veto.

For further reading here is the Bill: https://www.congress.gov/bill/115th-congress/senate-bill/722/text#toc-id2ab2e0cc7af146e299ac3e56a4b199f0

On Sunday, however, the White House said that Trump was open to signing legislation toughening sanctions on Moscow.

“We support where the legislation is now and will continue working with the House and Senate to put those tough sanctions in place on Russia until the situation in Ukraine is fully resolved and it certainly isn’t right now,” White House Press Secretary Sarah Huckabee Sanders said on the ABC program “This Week with George Stephanopoulos.” “The original piece of legislation was poorly written,” she added

The bill could throw up divisions with Europe as the new sanctions include fines for companies – of which there are several European firms – that help Russia to build a Baltic pipeline for Russian gas, an energy source relied upon in Europe. The European Commission is expected to discuss its response after the vote on Tuesday.

Markus Beyrer, director general of lobby group BusinessEurope, said in a statement Monday that “European business is extremely concerned by the imminent extension of the U.S. sanctions to Russia and the potential impact on the EU’s energy supply.”

“The EU heavily relies on external energy suppliers despite strong efforts to diversify and generate alternative sources. Russia is a key supplier of the EU. The potential and far-reaching extension of U.S. sanctions to Russia concentrated in the energy sector will have a strong impact on the EU’s energy supply. Ultimately business and consumers in the EU will pay the price.”

The move signifies another blow for President Trump given that the deal saw both Republicans and Democrats from the Senate and House of Representatives come together on Saturday to restrict the president’s powers.

The bill comes as investigations into possible alleged obstruction, meddling and collusion between Trump’s team and the Kremlin ahead of the 2016 election, are underway, and will be another obstacle to the president’s pursuit of warmer relations with Russia.

House Democratic Whip Steny H. Hoyer said in a statement on Saturday that he was pleased that both parties in the House and Senate “have reached agreement on sanctions legislation that will hold Russia and Iran accountable for their destabilizing actions around the world.”

“The legislation ensures that both the Majority and Minority are able to exercise our oversight role over the Administration’s implementation of sanctions… I look forward to seeing this legislation on the Floor next week, where I’m confident it will receive strong, bipartisan support.”

—Reuters contributed to this report.