The good news for President Obama is that there may be less to that deadline than meets the eye, which means the nuclear talks could continue for several more weeks before the Senate is in position to take a vote that Obama says could lead to war.

At issue is the patience of a group of Senate Democrats who say they’ll back new sanctions legislation if the administration can’t produce the outlines of a nuclear deal by March 24.

Iranian officials have said they’ll abandon the talks if Congress imposes additional sanctions.

Those Democrats came to Obama’s rescue in January, after the new Senate Republican majority prepared to move a sanctions bill sponsored by Republican Mark Kirk and Democrat Robert Menendez. President Obama vowed to veto the bill, but supporters claimed they might muster enough votes for a veto override.

After Obama officials pleaded for more time, 10 Senate Democrats agreed in writing to withhold their backing for the measure until March 24.

That is the day, the senators said, that the administration had promised to deliver a political framework that would spell out the broad parameters of a deal to halt Iran’s path to a nuclear bomb. The political deal would be followed by a final agreement featuring complex technical details that must be finished by June 30, the day the current interim pact with Iran expires.

But a close look at the calendar shows that, agreement or not on March 24, Congress will be hard-pressed to act right away. The Senate is scheduled to begin a two week recess three days later, with a planned return date of April 13.

Senate Republican leaders could quickly bring a sanctions bill to the floor if the administration can’t deliver a political agreement by the deadline. But Democrats are likely to filibuster the measure, and although Republicans are likely to muster the 60 votes needed to break a filibuster, it may not be possible to complete that process by week’s end. The challenge will be even tougher because the congressional calendar will be clogged with budget business.

The net result could be a precious extra three weeks of negotiating time for the U.S. and its five negotiating partners: France, Germany, Russia, China and Great Britain.

What’s more, Obama officials believe they may be able to count on a grace period from Senate Democrats, including the lead Democratic sponsor of the Iran sanctions bill, Robert Menendez of New Jersey, from whom other Democrats have taken their cues on Iran.

One source close to the talks said that Menendez has privately expressed a willingness to grant the talks some extra time if Obama officials can convince him they are close to a breakthrough. But Menendez has also insisted on tangible evidence of progress, beyond mere assurances from a White House with which he has an uneasy relationship.

That will be a challenge: Obama officials have refused to promise that they will produce an agreement in writing. Iranian negotiators are also said to be uncomfortable with putting their positions on paper.

Menendez’s spokesman, Adam Sharon, denied that the senator has promised any flexibility on the March 24 deadline, noting that Menendez firmly reiterated the date on the Senate floor last week after Senate Republicans sought to fast-track a different measure related to the nuclear talks. (That bill, introduced by Republican Senator Bob Corker, would require Obama to submit any Iran agreement to Congress for approval.)

“The deadline for a political framework agreement was announced by the administration and their negotiating partners, not the U.S. Congress,” Sharon said. “Senator Menendez will not allow for any further delays, nor is there a mechanism to allow for this deadline to slide, contrary to what unnamed sources may speculate.”

But some critics of the talks aren’t assuaged.

“People privately worry that Menendez and other pro-Israel Democrats will decide to not stick to the March 24 deadline and instead will once again give Obama even more time to cut a bad backroom deal with Iran,” said one senior congressional aide not authorized to speak for the record.

The nuclear talks, aimed at ensuring Iran remains at least a year away from being able to develop a nuclear weapon, have been extended twice since Secretary of State John Kerry struck an initial temporary accord in November 2013. The most recent extension, reached last November, promised a political agreement by March and a comprehensive deal that includes complex technical details by June 30.

The Kirk-Menendez bill would not impose sanctions on Iran right away. Instead, it would automatically impose them if Tehran abandons the nuclear talks or violates any of its agreements.

That could be enough to drive Iran from the bargaining table. “The entire deal is dead,” if Congress passes new sanctions, even delayed or triggered ones, Iranian Foreign Minister Javad Zarif said in December 2013.

Obama officials and many independent experts say that if Iran quits the talks, the risks of military confrontation will soar. In his January State of the Union address, President Obama vowed to veto the Kirk-Menendez bill, because “the American people expect us only to go to war as a last resort.”

An Obama White House spokeswoman was blunter in January of last year, saying of the legislation, “If certain members of Congress want the United States to take military action, they should be up front with the American public and say so.”

The deadline issue is further complicated by the fact that the Obama administration doesn’t accept the idea of a March 24 deadline for a political agreement — or that there even is a deadline. The State Department insists the relevant date is March 31, but a spokeswoman said last month that “we’ve never called it a deadline. We’ve called it a goal.” And instead of the words “agreement” or “deal,” Obama officials now speak of seeking an preliminary “understanding” with Tehran by month’s end.

“We believe we can get there by the end of March,” State Department spokeswoman Marie Harf said Friday.

But administration critics suspect the administration will try to buy more time for negotiations, and insist that the clock cannot be extended any further.

“U.S. negotiating leverage and deal demands have diminished because President Obama has not held Iran, and Congress has not held the president, to his own deadlines,” said Mark Dubowitz, executive director of the Foundation for the Defense of Democracies. “Another extension doubles down on a mistaken assumption that has plagued these negotiations, that further delays without increased leverage will improve the terms of a nuclear deal.”

As for Menendez, now bracing for possible federal corruption charges, he was defiant on the subject of Iran in remarks earlier this week to the American Israeli Public Affairs Committee.

“As long as I have an ounce of fight left in me… Iran will never have a pathway to a weapon,” Menendez said. “Not on my watch!”

“I will not yield,” he added, “to those who wish to break me.”