US State Department spokesperson Marie Harf said the diplomats held negotiations throughout Wednesday night until 6 a.m. Thursday morning.

“US Secretary of State John Kerry and his negotiating team back at work this morning," Harf said on Twitter.

French Foreign Minister Laurent Fabius rejoined the talks after he returned to Lausanne late on Wednesday.

Media reports cited Iranian Foreign Minister Mohammad Javad Zarif as saying on Thursday morning that "significant progress" has been made in the nuclear talks.

"It's likely to have a press statement today. If the efforts reach the conclusion today, we will have a joint press statement," the top negotiator told Iranian reporters ahead of Thursday's negotiations.

Two days after missing the March 31 deadline to close a framework agreement, the talks have extended to an eighth day.

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