John Kerry

State Department spokesman John Kirby says the flag will be hung early Monday morning before a ceremony to mark the re-opening of the Cuban embassy in Washington and the restoration of full diplomatic ties. 

The department's lobby features the flags of more than 150 other countries placed in alphabetical order. Cuba falls between Croatia and Cyprus in that arrangement.

Later on Monday, Secretary of State John Kerry will meet at the department with Cuban Foreign Minister Bruno Rodríguez after which they will hold a joint news conference, Kirby said.

9:05 a.m.

Russian President Vladimir Putin says the deal with Iran has brought the world "a sigh of relief."

In a statement published on the Kremlin website, Putin also said that "Russia will do its utmost to make sure that the Vienna agreement is fully implemented, thus contributing to the international and regional security."

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8:50 a.m.

After more than two weeks of intense and often combative talks that blew through three deadlines in Vienna and a weekend of deadlock, diplomats expressed optimism that a deal was at hand.

U.S. Secretary of State John Kerry, who on Thursday had threatened to walk away from the negotiations, note that "a few tough things" remain in the way of agreement but added: "We're getting to some real decisions."

With no agreement in sight, he may stay longer.

Kerry's trip to Vienna, now in its 15th day, already eclipses his own record for an overseas voyage and is the most extended stay outside the United States for a secretary of state since George Shultz in 1983. He will equal Shultz's mark on Sunday.

Kerry left Washington June 26 hoping the Iran talks would wrap before a June 30 deal deadline. Since then, negotiators have pushed off the deadline twice and did so for a third time Friday, allowing the negotiations to continue.

Kerry signaled that diplomats won't conclude an agreement with Iran over the coming hours — another delay that this time could complicate American efforts to quickly implement any deal.

The Iranians immediately fired back, accusing the U.S. and its European allies of causing the deadlock.

"We knew it would have been difficult, challenging, and sometimes hard," said Federica Mogherini, the European Union's foreign policy chief. Negotiations, she said, will continue for the next couple of days despite hitting some "tense" moments.

As the latest target date arrived for a deal setting a decade of restrictions on Iran's nuclear program, U.S. Secretary of State John Kerry, Iranian Foreign Minister Mohammad Javad Zarif and other top diplomats huddled in Vienna in search of a breakthrough. 

Diplomats confirmed the new development to the Associated Press on Saturday.

The annex, one of five meant to accompany the agreement, outlines which U.S. and international sanctions will be lifted and how quickly. 

Diplomats said senior officials of the seven-nation talks, which include U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif, still had to sign off on the package.

The announcement marks a major step in ending hostilities between the longtime foes.

The U.S. and Cuba have been negotiating the reestablishment of embassies following the Dec. 17 announcement that they would move to restore ties.

For Obama, ending Washington's half-century freeze with Cuba is seen as a major element of his foreign policy legacy. He has long touted the value of engagement and argued that the U.S. embargo on the communist island just 90 miles south of Florida was ineffective.

He will meet there with U.S. Secretary of State John Kerry in an attempt to resolve disputes that have forced an extension of the negotiations past the June 30 deadline.

Lavrov is to arrive Tuesday, the day that Iranian Foreign Minister Mohammad Javad Zarif returns to Vienna.

As Zarif flew home Sunday for consultations on how to proceed at the talks, a U.S. official confirmed that negotiators will miss a June 30 target date for a deal, aimed at limiting Tehran's nuclear program in exchange for sanctions relief.