Secretary of State John F. Kerry, left, and Iranian Foreign Minister Mohammad Javad Zarif are seen at nuclear negotiations on March 2 in Montreux, Switzerland. (Evan Vucci/AP)

Time is running out to forge an agreement on Iran’s nuclear program, which, though still a work in progress, is causing angst from Congress to the Knesset to many a majlis in the Middle East.

Secretary of State John F. Kerry flew to Paris on Saturday for consultations with the foreign ministers of France, Britain and Germany. Although the United States is taking the lead in negotiations, the three countries, plus China and Russia, are also involved in trying to frame a deal to constrict Iran’s nuclear ability, impose strict monitoring and possibly ease sanctions that began 10 years ago.

The reason that talks have come down to now-or-never is a self-imposed deadline. After limping along for most of a decade, talks picked up in earnest in 2013 after Hassan Rouhani was elected president of Iran on a promise of relief from sanctions. After two extensions in talks, negotiators are sprinting to reach a general understanding on basic principles by the end of March, leaving the complicated technical details to be worked out in the following three months.

Many in Congress have set the deadline at March 24, four months to the day after a temporary agreement was extended to June 30 and the United States said it wanted a general framework in place within four months. But the State Department is taking the deadline less literally, saying it is aiming for March 31.

Either way, the calendar pages are flipping past rapidly, leaving time for no more than two more rounds of talks.

Graphic: Iran's potential nuclear capability

[Read: Kerry seeks to assure Arab states over possible Iran nuclear deal]

Kerry and his Iranian counterpart, Foreign Minister Mohammad Javad Zarif, met over three days in Geneva this week even as Israeli Prime Minister Benjamin Netanyahu lobbied against the deal in a speech to a joint meeting of Congress.

Kerry and Zarif’s next meeting is scheduled for March 15, probably in Geneva. But the Iranian new year, Nowruz, begins March 22, a three-day national holiday when Kerry also has other obligations.

So unless they strike an agreement in Geneva, the talks will go down to the wire in a flurry of negotiations in the last days of the month. Then it will be up to President Obama to decide how to proceed.

If they succeed, a deal will be one of Obama and Kerry’s lasting legacies. Zarif and Kerry both emerge from every round of talks saying that progress has been made but that significant gaps remain. Kerry says it is now up to Tehran to decide whether it is willing to make concessions, facing down opposition from hard-liners who oppose negotiations with their arch enemy, the United States.

“We plan to return to the talks on the 15th of March, and we expect soon thereafter to know whether Iran will, in fact, be able to make the tough decisions that are required to get where we need to be,” Kerry said Thursday in Riyadh, the Saudi capital.

Administration officials have said negotiators are seeking to leave Iran with only one plant capable of enriching uranium, which is useful for both peaceful purposes and to build nuclear weapons. They also aim to have frequent and intrusive inspections by the International Atomic Energy Agency of all of Iran’s related plants, mills, mines and reactors, so the world can get a heads-up if Iran is cheating.

But many countries in the Middle East will not be easily assuaged by any agreement signed by a country that Kerry publicly acknowledged in Riyadh still will be considered a state sponsor of terror.

Israel in particular, considering Iran’s nuclear program a potential existential threat, is skeptical of administration assurances that the deal will require limits so that Iran would need a year or longer to “break out,” meaning amassing enough enriched uranium to build a nuclear bomb. Netanyahu told Congress that Israel calculates that the breakout time will be less than the Obama administration projects. Israel also is worried about what happens after the agreement ends 15 years or so down the road and Iran has no commitment to limit its nuclear program.

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