VIENNA (AP) — Pushing past a deadline, world powers and Iran extended negotiations for a comprehensive nuclear agreement by a week on Tuesday as the U.N. nuclear agency prepared to announce Tehran had met a key condition — significantly reducing its stocks of enriched uranium that could be used for atomic weapons.

Iran’s failure to comply would have severely undermined the negotiations, which are aimed at curbing the Iranians’ nuclear program for a decade in exchange for tens of billions of dollars in relief from international economic sanctions

The State Department announced the extra days of talks only hours before the expiration of the target date for their completion. Thoughts of meeting the deadline had been long-abandoned, but the extension has added significance as it holds in place nuclear restrictions that Iran agreed to some 20 months ago as well as slightly eased conditions for Iranian business with the world.

Those preliminary measures have been prolonged to next Tuesday “to allow more time for negotiations to reach a long-term solution,” spokeswoman Marie Harf said.? The statement came after U.S. Secretary of State John Kerry held a day of meetings in Vienna with the foreign ministers of Iran and Russia, and other key officials.

The day originally had been envisioned as the culmination of almost two years of secret and then public negotiations aimed at assuring the world Iran cannot produce nuclear weapons and providing the Iranian people a path of out of their international isolation. But officials said over the weekend they were nowhere near a final accord, and Iran’s foreign minister had flown back to his capital for further consultations amid increased signs of backtracking by his country’s supreme leader, Ayatollah Ali Khamenei.

As for Iran’s reduction in its stockpile of enriched uranium, diplomats said the country had removed a potential hurdle that nuclear experts had been watching closely over the past several weeks.

Uranium can be used to generate energy, or as the fissile core of a nuclear weapon, depending on its enrichment level. Under the preliminary deal from November 2013, Iran agreed to cap its stockpile of lower-enriched uranium at a little more than 7.6 tons and transform any remainder into a form that would be difficult to reconvert for arms use.

Although amounts were permitted to fluctuate, Iran had to come under the cap by Tuesday. And as of only a month ago, the U.N. nuclear agency reported the stockpile at more than 8 tons.

Iran’s compliance will be officially made public Wednesday in a new report by the Vienna-based International Atomic Energy Agency, said the diplomats, who weren’t authorized to speak publicly on the still-confidential report and demanded anonymity.

The weeklong extension has political overtones as well. An agreement by July 7 would give the Obama administration time to submit the deal to Congress by July 9. Congress would then have 30 days to review it, during which time President Barack Obama would not be able to ease sanctions.

If negotiations drag on past July 9 without a deal, that congressional review period would extend to 60 days. If lawmakers were to build a veto-proof majority behind new legislation enacting new economic sanctions or preventing Obama from suspending existing ones, the administration would be prevented from living up to an accord.

Talks in Austria’s capital restarted Tuesday after a one-day interruption, with Iran’s chief diplomat returning from Tehran and insisting he had a mandate to finalize a nuclear agreement. The promise came despite statements by supreme leader Khamenei in recent weeks that appeared to renege on a framework that his representatives agreed to three months ago in Lausanne, Switzerland.

The diplomacy has reached a “very sensitive stage” but progress is possible, Foreign Minister Mohammad Javad Zarif said. Asked by a reporter about his day of meetings at home, he said: “I already had a mandate to negotiate, and I am here to get a final deal and I think we can.” He returned with Iranian atomic energy chief Ali Akbar Salehi, who missed earlier sessions due to illness. Russian Foreign Minister Sergey Lavrov joined the gathering later Tuesday.

Significant disagreements persist, not least over the level of inspections on Iranian sites, how quickly the West would roll back sanctions and what types of research and development Iran would be permitted to conduct on advanced nuclear technology.

On Monday, U.S. officials had suggested backsliding by Tehran’s negotiators might need several more days to resolve.

Asked Tuesday if he was encouraged by the restart of talks, Kerry said only, “We had a good conversation.” The secretary of state, hobbled by a broken leg he suffered a month ago, has kept a low public profile since arriving in Austria last week.

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Associated Press writer George Jahn contributed to this report.