Iran and six world powers have made some progress during talks on ending the stand—off over Tehran’s nuclear programme, the US State Department said on Wednesday.

Both sides have been trying to agree on an agenda and timetable for the diplomatic process in the months ahead at the talks in Vienna, which are scheduled to end on Thursday.

“We do think that we have made some progress over these last few days, and hopefully we can to continue to build on that going forward,” State Department spokeswoman Marie Harf said, without clarifying whether a framework was likely to be agreed by Thursday.

The aim of the diplomatic process is to reach a comprehensive deal that would restrict uranium enrichment and other nuclear activities in Iran for several years to decrease the possibility that the country uses its civilian programme to make weapons.

In return, the world powers would lift all sanctions against Tehran.

The deal would build on an interim agreement reached in November in Geneva, which runs until July and has already resulted in the suspension of some sanctions and a limited cut—back in uranium enrichment.

“The meetings have been good and constructive so far. We are still working on the agreement (on a talks framework),” Iranian Deputy Foreign Minister Hamid Baeidinejad said on the second day talks with Britain, China, France, Russia, the United States and Germany.

Iran’s Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Catherine Ashton, who acts as lead negotiator of the six powers, were expected to hold a press conference Thursday.

Mr. Zarif expressed optimism about reaching an comprehensive agreement.

“A solution within six months is not unrealistic,” Zarif said.

Both sides agreed in Geneva to conclude a final deal within six months, but they also made allowance for the possibility that the talks may be extended by up to a year.

Some Western diplomats have said that six months is not a realistic timeframe, given how far apart both sides are on key issues.

Western powers are suggesting that Iran should dismantle some nuclear facilities as part of the deal and that Tehran’s ballistic missile programme should be part of the discussions. Iranian negotiators have rejected both ideas.

While the international community is worried that Iran might use uranium and plutonium from its civilian nuclear installations to build nuclear weapons, the Islamic republic denies having such aims.

Iranian President Hassan Rowhani is under pressure to get the oil embargo and other crippling sanctions lifted as soon as possible in order to revive the economy.

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