When asked on Sept. 20 whether the U.S. will withdraw from the Iran nuclear deal, President Trump said he had made a decision but declined to reveal it. "I'll let you know," he said. (The Washington Post)

President Trump said on Wednesday that he has decided what to do about the Iran deal, which he has strongly and repeatedly criticized. But he left a cliffhanger about what that decision will be.

Speaking in New York after a meeting with Palestinian Authority President Mahmoud Abbas, Trump responded to a reporter's question about whether a decision had been made about the future of the deal.

“I have decided,” Trump said, three times.

Pressed by reporters to reveal his decision, Trump smiled and said, "I’ll let you know what the decision is.”

The comments come a day after Trump said in a speech to the United Nations that the deal was “one of the worst and most one-sided transactions the United States has ever entered into.”

“Frankly, that deal is an embarrassment to the United States, and I don't think you've heard the last of it, believe me,” he added. Despite the criticism, the Trump administration has not yet moved to decertify the agreement negotiated by the Obama administration.

Iran has insisted that it has lived up to the requirements of the agreement. Speaking Tuesday to media executives, Iranian President Hassan Rouhani said that if the United States reneges on the deal, it, not Iran, will be seen as untrustworthy.

“Everyone will clearly see that Iran has lived up to its agreements and that the United States is therefore a country that cannot be trusted,” he said. “We will be the winners,” while the United States “will certainly sustain losses.”

And in a series of tweets on Wednesday morning, Rouhani doubled down, sharply criticizing Trump for his UN speech and his insistence on undermining the Iran deal. In one message, he referred to Trump as  "rogue" newcomer to politics.

"Destruction of #JCPOA by 'rogue' newcomers to the world of politics will never impede Iran’s course of progress and advancement," Rouhani tweeted, referring to the deal by its official name "Joint Comprehensive Plan of Action." "By violating its international commitments, the new U.S. administration only destroys its own credibility for future negotiations."

"Iran won't be the first country to violate the agreement but it will respond decisively and resolutely to its violation by any party," he added.

Carol Morello contributed to this report.