The White House on Monday denied reports that Iran has backed out of an agreement to ship nuclear material out of its country as part of a broader agreement with Western powers.

“The idea that there had been an agreement that Iran had backed away from in the last 24 hours is not true,” White House deputy press secretary Eric Schultz told reporters, according to The Washington Times.

“In terms of what’s going to happen with that stockpile, that is something our negotiators are working through, but it’s not accurate to say there had been an agreement that was then backtracked,” he added.

U.S. officials said ealier Monday they were still negotiating with their Iranian counterparts on how to dispose of Iran’s nuclear stockpile and said shipping the atomic fuel out of the country was still a possibility.

On Sunday, however, Iran’s deputy foreign minister, Abbas Araqchi, clarified that Tehran does not intend to send stockpiles of enriched uranium abroad.

As talks go down to the wire with a deadline on Tuesday, Schultz said President Obama is still willing to walk away from a bargain.

“The president has made clear that he’s not going to take a bad deal. … It’s going to be up to the Iranians in order to make some tough decisions as the deadline approaches,” he said.

Iran and the six world powers are trying to turn an interim agreement signed in 2013 into a permanent one. On Sunday reports emerged that a provisional agreement on key elements of Iran’s nuclear program had been reached, but Iran denied those reports.

Earlier Monday, Deputy State Department spokeswoman Marie Harf said that “now is really the time to make the decisions”, but also said the United States was not too optimistic that a deal would be reached by Tuesday, despite it being the deadline.

“I don’t want to predict what the outcome will be,” Harf said. “We still see a path to get a political understanding. There is still a path to do this. I would probably say (a) 50-50 chance we will get it done.”