VIENNA - A senior U.S. official acknowledged Sunday that Iran nuclear talks will go past their June 30 target date, as Iran's foreign minister prepared to head home Sunday for consultations before returning to push for a breakthrough.
Iranian media said Mohammed Javad Zarif's trip was planned in advance. Still, the fact that he was leaving the talks so close to the Tuesday deadline reflected his need to get instructions on how to proceed on issues where the sides remain apart - among them how much access Tehran should give to U.N. experts monitoring his country's compliance to any deal.
The United States insists on more intrusive access than Iran is ready to give. With these and other disputes still unresolved the likelihood that the Tuesday target deadline for an Iran nuclear deal could slip was increasingly growing even before the U.S. confirmation.
U.S. Secretary of State John Kerry was in Vienna again for the talks. CBS News correspondent Margaret Brennan reports Kerry is under pressure to deliver President Obama's chief foreign policy goal - a nuclear accord with Iran.
Several former Obama aides warned in a recent letter that the emerging deal "may fall short of meeting the administration's own standard of a 'good' agreement."
German Foreign Minister Frank-Walter Steinmeier and French Foreign Minister Laurent Fabius are currently in Vienna, and their Russian and British counterparts are to join later. China was sending a deputy foreign minister in a building diplomatic effort to wrap up the negotiations.
For weeks, all seven nations at the negotiating table insisted that Tuesday remains the formal deadline for a deal. But with time running out, a senior U.S. official acknowledged that was unrealistic.
"Given the dates, and that we have some work to do ... the parties are planning to remain in Vienna beyond June 30 to continue working," said the official, who demanded anonymity in line with State Department practice.
Asked about the chances for a deal, Federica Mogherini, the European Union's top diplomat, told reporters: "It's going to be tough ... but not impossible."
Steinmeier avoided reporters but told German media earlier: "I am convinced that if there is no agreement, everyone loses."
"Iran would remain isolated. A new arms race in a region that is already riven by conflict could be the dramatic consequence."
Both sides recognize that there is leeway to extend to July 9. As part of an agreement with the U.S. Congress, lawmakers then have 30 days to review the deal before suspending congressional sanctions.
But postponement beyond that would double the congressional review period to 60 days, giving both Iranian and U.S. critics more time to work on undermining an agreement.
Arguing for more time to allow the U.S. to drive a harder bargain, Israeli Prime Minister Benjamin Netanyahu - a fierce opponent of the talks - weighed in on Sunday against "this bad agreement, which is becoming worse by the day."
"It is still not too late to go back and insist on demands that will genuinely deny Iran the ability to arm itself with nuclear weapons," he said.
The goal of the talks involving Iran and the U.S., Britain, China, France, Germany and Russia is a deal that would crimp Tehran's capacity to make nuclear weapons in exchange for sanctions relief. Iran insists it does not want such arms but is bargaining in exchange for sanctions relief
On Saturday, diplomats told The Associated Press that Iran was considering a U.S.-backed plan for it to send enriched uranium to another country for sale as reactor fuel, a step that would resolve one of several outstanding issues.