Cairo: Iran and the US kicked off Sunday a new round of nuclear talks with Secretary of State John Kerry saying it was time to finish the job and agree to a deal after 18 months of intense negotiations.
"If (Iran`s nuclear programme is) peaceful, let`s get it done. And my hope is that in the next days, that will be possible," Kerry told CBS television in Egypt on Saturday.
On Sunday he arrived to join the talks in the Swiss lakeside city of Lausanne, and was on Monday expected to meet Iranian Foreign Minister Mohammad Javad Zarif, the State Department said.
Later Monday Zarif was due to travel to Brussels to meet his British, French, German and EU counterparts before returning to Lausanne.
Kerry, under major pressure in Washington not to strike a soft agreement, wants Iran to dramatically scale down its nuclear programme in order to make it much more difficult to develop atomic weapons.
Zarif, himself under pressure from hardliners to get painful sanctions eased, says Iran`s atomic programme is for purely peaceful purposes. Tehran wants to expand its activities.
The target is for Iran and six world powers -- the US, Russia, China, Britain, France and Germany -- to agree the outlines of a deal by March 31 and to fine-tune the details by July 1.The nuclear standoff has lasted more than a decade, but the 2013 election of President Hassan Rouhani resulted in a minor thaw and the past 18 months have seen an unprecedented diplomatic effort.
Under a landmark November 2013 interim deal, Tehran stopped expanding its activities in return for minor sanctions relief.
Since then the parties have been pushing for a lasting accord.
But to the alarm of Israel, US Republicans and Washington`s Gulf allies, the US looks to have abandoned insisting that Iran dismantle all nuclear activities.
Instead it appears prepared to tolerate a small programme under tight controls and potentially shipping abroad Iran`s nuclear material, possibly to Russia.
In theory this still leaves Iran with the possibility, however small, to get the bomb, critics say.
Last week 47 Republicans took the explosive step of writing an open letter to Iran`s leaders.
They warned that any nuclear deal could be modified by Congress or revoked "with the stroke of a pen" by whomever succeeds President Barack Obama, a Democrat.
It followed a barnstorming address to US lawmakers on a Republican invitation by Israeli Prime Minister Benjamin Netanyahu -- who faces a battle to be re-elected Tuesday -- against a deal.
The letter provoked a storm in Washington with Obama saying he was "embarrassed" for the signatories, while Zarif said it "told us that we cannot trust the United States."
The Obama administration has been trying to dissuade lawmakers from passing a law, called Corker-Menendez, that would force the president to submit any Iran deal to Congress for approval.
Obama is sure to veto any such legislation but the Republicans are trying to assemble a two-thirds majority in both houses of Congress to pass the measure and override the veto.
"Apparently the administration is on the cusp of entering into a very bad deal with one of the worst regimes in the world that would allow them to continue to have their nuclear infrastructure," Senate Majority Leader Mitch McConnell Sunday told CNN.Some progress has been made towards a deal but the two sides remain far apart on several key issues.
These include the future size of Iran`s uranium enrichment capacities -- which can make nuclear fuel but also the core of a bomb -- the pace at which sanctions would be lifted and the accord`s duration.
"We need clarity on the way in which sanctions will be lifted and what the guarantees will be for applying the deal," Zarif told state television Sunday from Lausanne.
Two deadlines, in July and November, passed without an agreement but in view of the controversy in Washington -- and pressure in Iran on Rouhani to deliver -- extending yet again will be very tough.
"Absent a tangible achievement by the end of this month, the process could succumb to outside pressures," International Crisis Group analyst Ali Vaez told AFP.
The White House said Sunday meanwhile that any deal would need approval from the UN Security Council.
Senior negotiator Abbas Araqchi said political directors from all six powers will be present in Lausanne from Tuesday.