By GEORGE JAHN AND BRADLEY KLAPPER, ASSOCIATED PRESS

The end of Western sanctions against Iran loomed Saturday as Iran's foreign minister suggested the U.N. atomic agency is close to certifying that his country has met all commitments under its landmark nuclear deal with six world powers.

Iranian Minister Mohammad Javad Zarif held a series of meetings with his European Union and U.S. counterparts — including U.S. Secretary of State John Kerry — on implementing the accord.

"All oppressive sanctions imposed against Iran will be annulled today," Zarif said on Iranian state TV — a reference to the process that will end financial and other penalties imposed on his country once the U.N. agency says Tehran has fulfilled its obligations to restrict its nuclear programs.

But even as diplomatic maneuvering on the nuclear issue dragged on into the evening, progress came on another area of Iran-U.S. tensions: U.S. and Iranian officials announced that Iran was releasing four detained Iranian-Americans in exchange for seven Iranians held or charged in the United States.

U.S. officials said the four Americans, including Washington Post reporter Jason Rezaian, former Marine Amir Hekmati and pastor Saeed Abidini, were to be flown from Iran to Switzerland on a Swiss plane and then brought to a U.S. military hospital in Landstuhl, Germany, for medical treatment. There were conflicting reports about the name of the fourth American freed.

In return, the U.S. will either pardon or drop charges against seven Iranians — six of whom are dual citizens — accused or convicted of violating U.S. sanctions. The U.S. will also drop Interpol "red notices" — essentially arrest warrants — on a handful of Iranian fugitives it has sought.

Rezaian is a dual Iran-U.S. citizen convicted of espionage by Iran in a closed-door trial in 2015. The Post and the U.S. government have denied the accusations, as has Rezaian.

In Vienna, a senior diplomat familiar with the nuclear deal said last-minute discussions between French and U.S. officials on what Iran needed to do to restrict its nuclear research under the deal appeared to be responsible for the delay Saturday in lifting sanctions. He demanded anonymity because he was not authorized to discuss the diplomacy.

A State Department official said "some technical clarifications" were taking place but added: "There is no major issue being fought over." The official demanded anonymity in line with State Department practice.

Responding to the delay, Zarif, in a tweet, said: "Diplomacy requires patience."

Certification by the International Atomic Energy Agency would allow Iran to immediately recoup some $100 billion in assets frozen overseas. The benefits of new oil, trade and financial opportunities from suspended sanctions could prove far more valuable for Tehran in the long run.

Kerry and EU foreign policy chief Federica Mogherini were in Vienna, headquarters to the IAEA, for separate meetings with Zarif.

Despite Zarif's optimistic comments about the approaching end to sanctions, both he and Kerry deflected a question about whether their deal would be implemented later in the day.

"We're trying," said Zarif.

"We're working on it," added Kerry, seated across the table from Zarif in an ornate room at a luxury Vienna hotel.

In his earlier comments to Iranian television, Zarif said the deal between his country and the six world powers would hold, telling Iranian media that all parties would "not allow the outcome of these talks to be wasted."

The agreement, struck after decades of hostility, defused the likelihood of U.S. or Israeli military action against Iran, something Zarif alluded to.

"Our region has been freed from shadow of an unnecessary conflict that could have caused concerns for the region," he said. "Today is also a good day for the world. Today will prove that we can solve important problems through diplomacy."

Iran insists all of its nuclear activities are peaceful. But under the July 14 deal, Iran agreed to crimp programs which could be used to make nuclear weapons in return for an end to sanctions. The agreement puts Iran's various nuclear activities under IAEA watch for up to 15 years, with an option to re-impose sanctions should Tehran break its commitments.

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Associated Press Writer Ali Akbar Dareini contributed from Tehran