Senior envoys from Iran and six world powers met for a new round of negotiations on Tuesday, in an effort to reach a broad agreement on scaling back Iran’s nuclear programme and lifting sanctions by July.

Iran’s President Hassan Rowhani is under pressure to see the crippling sanctions against his country lifted, while US Republicans gearing up for Congressional mid—term elections in November are pushing President Barack Obama to take a tough stance on the issue.

Adding more urgency is the expected end—of—year departure of EU foreign policy chief Catherine Ashton, the chief negotiator for Britain, China, France, Russia, the United States and Germany.

“We’re trying as hard as we can to drive the process forward,” Ashton’s spokesman Michael Mann said in Vienna. “We’re engaged in very detailed and substantial negotiations at this point.” Both sides in the talks have said they want to start drafting the agreement next month.

However, Iran and the six powers have yet to agree on the limits that Tehran will have to accept on its enrichment programme, and on the future of the plutonium—producing Arak reactor, Iranian and Western diplomats have said.

The six powers are concerned that Iran could use enriched uranium or plutonium to make nuclear weapons. Iranian leaders insist they are only interested in nuclear energy and scientific applications.

Iran’s Deputy Foreign Minister Majid Takht Ravanchi said his delegation was considering proposals on Arak, which is still under construction.

“We have not reached a conclusion on Arak but at least we know very well where they are and where we are and how the positions of the two sides can merge,” he told the Wall Street Journal.

Western officials have said one option would be to convert Arak into a type of reactor that does not produce plutonium as a side product.

Iranian officials have proposed instead that countries such as Germany, France, Japan, Brazil or Argentina join the Arak research reactor project, to guarantee that it serves peaceful purposes.

Ravanchi also said that nuclear inspections that are to be part of the final agreement were on the agenda of talks this week.

Iran and the six powers have been implementing a preliminary agreement since January, under which Tehran has slowed down its drive to enrich uranium and halted construction at Arak, while some Western sanctions have been suspended.

As part of that preliminary deal that was signed in November, US aircraft maker Boeing announced last week that it would resume supplying spare parts for Iran’s ageing fleet.

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