WASHINGTON (Reuters) - U.S. lawmakers signaled they plan to ensure the United States complies with the 2015 Iran nuclear deal despite U.S. President Donald Trump s misgivings about the pact, the European Union s foreign policy chief said on Tuesday.  I got clear indications that the intention is to keep the United States compliant with the agreement,  the EU s Federica Mogherini said at a press conference on a visit to Washington. Trump on Oct. 13 dealt a blow to the pact by refusing to certify that Tehran was complying with the accord even though international inspectors said it was. Under the deal Iran agreed to curb its nuclear program in return for relief from economic sanctions. Trump s decision has thrown into doubt the future of the pact negotiated by Iran, the EU and six major powers - Britain, China, France, Germany, Russia and the United States. Congress has until mid-December to decide whether to reimpose sanctions lifted under the deal, something few diplomats expect. Mogherini sought to avoid publicly becoming embroiled in the U.S. congressional debate about what kind of legislation, if any, to pass even as she stressed the EU s desire to see the United States stick with the nuclear agreement.  I made clear any outcome of any process ... has to be, at the end of the day, compliant with the deal,  Mogherini said. She said she had voiced her readiness to help lawmakers  find solutions that are compatible  with U.S. compliance under the agreement. Separately, the head of the U.N. nuclear watchdog told reporters it would be  a pity  if Iran were to cease to provisionally implement the Additional Protocol, which gives the agency more tools to verify a country s nuclear compliance.  The Additional Protocol is the most ... important tool for us in the verification. So if it happens, it s a pity,  said     International Atomic Energy Agency Director General Yukiya Amano. Under the 2015 deal, Iran agreed to provisionally implement the Additional Protocol. Amano told reporters that if Iran were to discontinue the protocol, the IAEA would not be able to get access to undeclared potential nuclear sites. Amano said that on a visit to Iran last month, Iranian officials had assured him they would continue implementing the nuclear deal and would not be the first to abandon it. The Additional Protocol was created in the 1990s as a way to smoke out covert, arms-related activities after the discovery of Iraq s secret nuclear weapons program and revelations that North Korea and Romania had separated plutonium. Asked if the Iranians had given him any sign that they might abandon the Additional Protocol, Amano replied:  They don t say what will happen, but anything can happen. That is my sense.  