By Parisa Hafezi and Fredrik Dahl
VIENNA (Reuters) - U.S. Secretary of State John Kerry met his Iranian counterpart on Monday for a second day to push for "critical choices" on Tehran's nuclear programme with both sides complaining that scant progress has been made ahead of a July 20 deadline.
Kerry and Mohammad Javad Zarif met for two hours on Sunday on the sidelines of talks between Iran and six major negotiating powers - the United States, Britain, France, Germany, Russia and China - with the deadline for a deal just a week away.
In his bilateral meetings with Zarif, Kerry wants to "gauge Iran's willingness to make the critical choices it needs to make", a senior State Department official said.
"The Secretary will take the time necessary to have that discussion, and that's why they will be meeting again today, to see if progress can be made," the official said.
A State Department official said Kerry and Zarif were in talks in the Palais Coburg in the centre of Vienna and it was unclear how long their meeting would last.
Kerry said on Sunday there were still substantial gaps with Iran on how to reduce its nuclear fuel-making capacity, a view that Iranian and other Western officials echoed.
Earlier, a senior U.S. official said Iran was sticking to "unworkable and inadequate" positions.
The six powers want Iran to reduce its nuclear fuel-making capacity to deny it any means of quickly producing atom bombs. In exchange, sanctions that have crippled the large OPEC member's oil-dependent economy would gradually be lifted. Iran says it is enriching uranium for peaceful energy purposes only and wants the sanctions removed swiftly.
But a history of hiding sensitive nuclear work from U.N. inspectors has kept international suspicions high and heightened the risk of a new Middle East war should diplomacy fail to yield a long-term settlement.
Zarif said on Sunday after his meeting with Kerry that "our team is ready to work with full speed during the seven remaining days in order to reach a comprehensive deal that can be acceptable for both sides."
But with the two sides so far apart there was little optimism that an agreement could be signed by next Sunday. The thorniest issue, diplomats close to the talks say, is the size of Iran's future enrichment programme.
"It will be difficult to have an agreement in a week," a senior Western diplomat told reporters. "The Iranians would have to budge on the key issues and very quickly. There are a lot of technical aspects that would be difficult to complete in a week."
There is a possibility that the talks on a long-term settlement to end the decade-long dispute could be extended for as long as six months.
A Nov. 24 preliminary agreement between Iran and the six powers included a provision for lengthening talks on a permanent agreement as far out as next January if all sides agree. But even an extension would have to be negotiated.
A senior U.S. official said on Saturday that an extension would be difficult to consider without first seeing "significant progress on key issues".
Western officials have said that major issues include enrichment, Iran's stockpiles of nuclear material and answering U.N. inspectors' questions about its past atomic research that Western powers and analysts suspect was linked to weapon-making. French Foreign Minister Laurent Fabius on Sunday publicly raised the possibility of extending the talks, though British Foreign Secretary William Hague said it was too early to discuss the idea of an extension.
German Foreign Minister Frank-Walter Steinmeier told reporters that Germany and the other members of the group have used all their powers of persuasion to convince Iran of the urgency of a proper deal in the coming days.
"This may be the last chance for a long time to peacefully resolve the dispute over Iran?s nuclear programme," he told reporters. "It's now up to Iran to decide whether it wants cooperation with the international community or to remain in isolation. ... The ball is in Iran's court."
(Additional reporting by Lesley Wroughton, Louis Charbonneau and John Irish; Writing by Louis Charbonneau; Editing by Louise Ireland)