Major powers, Iran extend interim deal to July 7

From left, US National Security Council Senior Director for Iran, Iraq, Syria and the Gulf States Robert Malley, US Secretary of Energy Ernest Moniz, US Secretary of State John Kerry and U.S. Under Secretary for Political Affairs Wendy Sherman attend the Iran nuclear talks at a hotel in Vienna, Austria on June 30, 2015.
Siamek Ebrahimi | Anadolu Agency | Getty Images

The Iranian interim nuclear accord originally scheduled to close by the end of this month has been extended until July 7, the U.S. delegation announced on Tuesday. The extension will allow for more time to negotiate the terms of a final deal. (Tweet this)

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A preliminary agreement was reached two months ago, but since then it had appeared not enough progress was made. The market had expected an extension.

"The P5+1 and Iran have decided to extend the measures under the Joint Plan of Action until July 7 to allow more time for negotiations to reach a long-term solution ... on the Iran nuclear issue," Marie Harf, senior adviser for strategic communications at the U.S. State Department, said.

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The so-called "P5+1" are the six major powers negotiating with Iran—Britain, China, France, Germany, Russia and the United States.

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Iranian Foreign Minister Mohammad Javad Zarif was rejoining the talks Tuesday after consultations in Tehran and was to meet U.S. Secretary of State John Kerry. Zarif arrived in Vienna with Ali Akbar Salehi, the head of Iran's atomic agency, who had missed earlier sessions due to illness. Iran's official news agency said Salehi's participation indicated Iran's serious desire to accelerate the talks and achieve a comprehensive deal. Russian Foreign Minister Sergey Lavrov was also expected to join the discussions.

On Monday, U.S. officials suggested that significant backtracking by Tehran's negotiators may need several more days of discussions to resolve.

—CNBC's Patti Domm, the AP and Reuters contributed to this report.