WASHINGTON (Reuters) - As Congress faces a possible fight over the future of the Iran nuclear agreement, senior Senate Democrats demanded on Wednesday that the Trump administration provide lawmakers with any information showing Tehran is not complying with the international pact. In a letter to Secretary of State Rex Tillerson, Defense Secretary Jim Mattis and other Cabinet officials first reported by Reuters, the lawmakers said the administration had not provided any such information, as is required under the 2015 Iran Nuclear Review Act. Republican President Donald Trump has long criticized the nuclear agreement, one of the signature foreign policy achievements of his Democratic predecessor, Barack Obama. In a speech at the United Nations on Tuesday, Trump blasted the deal reached by the United States, five other world powers and Iran, known as the JCPOA. He called it an  embarrassment to the United States.  Trump is facing a mid-October deadline for certifying whether Iran is still complying with the JCPOA, in which Iran agreed to curb its nuclear program in exchange for sanctions relief. On Wednesday, a senior U.S. official said Trump was leaning toward not certifying that Iran is complying with the pact, and letting Congress effectively decide whether to kill the agreement. The 2015 Iran Nuclear Review Act gives Congress the right to vote on whether to reimpose sanctions suspended under the JCPOA, once the president decides to decertify. The law also requires, however, that the president formally notify Congress of any evidence he has to justify that decision. While Wednesday s letter was signed only by Democrats, even some of Trump s fellow Republicans have questioned the wisdom of breaking from the agreement, unless Trump can provide concrete evidence that Iran is not complying with it. Congressional aides from both parties also said leaving the agreement seemed unnecessary, especially when Washington needs to work with international partners on complicated issues like North Korea s nuclear weapons and ballistic missiles program and the civil war in Syria and refugee crisis. Ed Royce, the Republican chairman of the House of Representatives Foreign Affairs Committee, said on CNN after Trump s U.N. speech that the United States should stay in the Iran deal, but  enforce the hell out of it.   The Democrats  letter on Wednesday noted that the 2015 review act required the president to provide information to Congress on any Iranian breach of the agreement or compliance concern within 10 days of receiving the information.  To date, the Senate has received no such notification and the Administration has provided little public testimony to Congress on the status of Iranian compliance with the agreement,  the letter said. The letter asked the administration to provide a written report and, where appropriate, public testimony to Senate committees, before Oct. 6, if it is aware of any information suggesting Iran is not complying or that would lead Trump to conclude that the continued suspension of sanctions is not in the U.S. national security interest. The letter to Tillerson, Mattis, Treasury Secretary Steve Mnuchin, Energy Secretary Rick Perry and Director of National Intelligence Dan Coats was signed by Senators Sherrod Brown, Maria Cantwell, Ben Cardin, Richard Durbin, Patrick Leahy, Jack Reed and Mark Warner. 