WASHINGTON (Reuters) - U.S. President Donald Trump will strike a blow against the 2015 Iran nuclear agreement on Friday in defiance of other world powers, choosing not to certify that Tehran is complying with the deal in a major reversal of U.S. policy. Trump’s decision will not withdraw the United States from the agreement, which was negotiated by Washington and other world powers during the administration of former President Barack Obama. The move likely gives U.S. lawmakers 60 days to decide whether to bring back sanctions on Iran that were lifted under the deal.   If Congress reimposes the sanctions, the United States would in effect be in violation of the terms of the nuclear deal and it would likely fall apart. If lawmakers do nothing, the deal remains in place. Here is a look at where key U.S. lawmakers stand on the deal:  SENATE MAJORITY LEADER MITCH MCCONNELL: Like every Republican in Congress, McConnell voted against the Iran nuclear agreement. He has not expressed a position on how he will respond to Trump’s decertification, but has not yet broken from Trump on policy matters. HOUSE OF REPRESENTATIVES SPEAKER PAUL RYAN: Has not said where he stands. “I don’t want to get ahead of the president,” he said last week. HOUSE MAJORITY LEADER KEVIN MCCARTHY: Has not said what he would do. SENATE FOREIGN RELATIONS COMMITTEE CHAIRMAN BOB CORKER: Repeatedly spoke out against the agreement and wrote legislation that gave Congress some say over it. While he has questioned Trump recently on some foreign policy issues - helping spark a Twitter feud - Corker has followed the administration line on most policy matters. Corker said on Friday he expected to introduce legislation to “address flaws” in the pact without violating it.  HOUSE FOREIGN AFFAIRS COMMITTEE CHAIRMAN ED ROYCE: Royce says “As flawed as the deal is, I believe we must now enforce the hell out of it.” It was not clear how he would respond to the legislation.  SENATE MINORITY LEADER CHUCK SCHUMER: Opposed the deal two years ago but more recently says it should be left in place but strongly enforced with efforts to clamp down on other activities like Iran’s ballistic missile program. HOUSE MINORITY LEADER NANCY PELOSI: Supported the original deal, still supports it. SENATE FOREIGN RELATIONS COMMITTEE TOP DEMOCRAT BEN CARDIN: Opposed the deal two years ago, but says U.S. should honor it now, while strictly enforcing it and clamping down on other Iranian activities detrimental to the interests of the United States and its allies. HOUSE FOREIGN AFFAIRS TOP DEMOCRAT ELLIOT ENGEL: Opposed the deal two years ago but said killing it now would be a “grave mistake.” Still an Iran hawk on issues such as Tehran’s ballistic missile program, human rights violations and its support for what Washington sees as terrorism.           