REUTERS

President Donald Trump, who lambasted the 2015 pact as a candidate, gave himself more time to decide whether to scuttle it or let it stand, ABC News reported.

Instead, senior Trump administration officials sought to emphasize their deep concerns about Iran's non-nuclear behavior and vowed that those transgressions won't go unpunished.

Read alsoTrump administration debating whether to withdraw from disarmament pact with Russia – mediaIn a shift from Trump's previous threat to "rip up" the deal, officials said the administration was working with U.S. allies to try to fix the deal's flaws, including the expiration of some nuclear restrictions after a decade or more. The officials also said the U.S. would slap Tehran with new sanctions penalizing it for developing ballistic missiles and other activity.

Trump, Secretary of State Rex Tillerson and "the entire administration judge that Iran is unquestionably in default of the spirit" of the agreement, one official said. That assessment carries no legal force, while Trump's certification that Iran is technically complying clears the way for sanctions to remain lifted.

The late-night announcement capped a day of frenzied, last-minute decision-making by the president, exposing deep and lingering divisions within his administration about how to deal with a top national security issue.

Since early last week, Trump's administration had been prepared to make the certification, a quarterly requirement. Trump first told Congress in April that Iran was indeed complying. With no final decision on his broader Iran policy, the White House had planned to let the status quo stand for another three months.

As planned, a public rollout began Monday morning involving close choreography among the White House, the State Department and other parts of government. The White House National Security Council distributed talking points to other agencies while national security adviser H.R. McMaster and Treasury Secretary Steven Mnuchin briefed outside policy experts who frequently comment on such issues in the media.

Then, just as the White House was preparing to brief reporters, the announcement was abruptly halted and the talking points temporarily recalled as the president reconsidered the decision, according to officials and others briefed by the administration. Among the options Trump discussed with Tillerson and other aides was to extend the sanctions relief but refuse to certify Iran's compliance, several officials said.

With a midnight deadline just hours away, officials disclosed the final decision to reporters on a chaotic conference call on the condition that it not be published until the White House had a chance to formally notify Congress.