Negotiations to halt Iran's nuclear weapons program have been extended through late November after negotiators from Iran and six world powers failed to reach an agreement in Vienna by the Sunday deadline.

Deliberations have been on and off since January as negotiators have tried to reach a deal that would keep Iran from developing a nuclear weapon and relieve economic sanctions placed on the oil-rich Islamic republic, The Washington Post reported.

The negotiators agreed Friday to extend the deadline to Nov. 24 because of several issues that weren't resolved, European Union foreign policy chief Catherine Ashton and Iranian Foreign Minister Mohammad Javad Zarif said in a joint statement.

"There are still significant gaps on some core issues, which will require more time and effort," according to the statement.

Ashton and the Iranian diplomat have led the six world powers, including the U.S., in the negotiations and said "tangible progress" had been made. They also said some discussions have been on the final agreement's draft text.

Sources close to the negotiations said the most recent round of discussions, which began July 2, increased the likelihood a deal could be reached. However, it is unclear when the talks to end the decade-long standoff would recommence.

A precondition of the deal was that Iran would be allowed to keep a "robust" amount of its uranium enrichment for domestic nuclear capabilities, which has become a point of national pride. The country's leaders cited Western nations' ability to use nuclear technology and insisted it should be allowed to as well.

Although negotiations have made some headway, they have gotten stuck over how much Iran could retain its current program. The U.S. and European nations fear that Iran could divert its program to nuclear weapons again even after a deal is reached.

"We are committed to testing whether we can address one of the world's most pressing priorities -- ensuring that Iran does not obtain a nuclear weapon," Secretary of State John Kerry said in an issued statement. "This effort remains as intense as it is important, and we have come a long way in a short period of time."

If an agreement can be made by the November deadline, President Barack Obama will then have to convince Congress that a solid deal has been brokered in order to approve the removal of U.S. sanctions on Iran.

Last fall, the U.S. and Iran reached a temporary agreement, which placed a large cap on Iran's nuclear program during the negotiations, and will continue during the four-month extension. Under the agreement, Iran has also been given $3 billion in sanctions relief, though it will no longer be given funding during the extended talks.

Related