US Secretary of State John Kerry has defended moves to strike a nuclear deal with Iran and said "war should be the last resort" to resolve the dispute.
"If we had to turn to a military option, because we are left no other option, we must show the world we have exhausted every possible remedy and opportunity." Kerry told reporters in Abu Dhabi on Monday.
While saying that a deal with Iran was expected within months, Kerry tried to reassure Washington's Arab allies and Israel that his country would not abandon them.
He denied reports of rifts among the powers and suggested Iran was not ready to accept the plan at that point.
"The P5+1 [five permanent members of the UN Security Council plus Germany] was unified on Saturday when we presented our proposal to the Iranians... But Iran couldn't take it, at that particular moment they weren't able to accept," he said.
His comments came as France said world powers were close to an agreement with Iran on its disputed nuclear drive, despite failure to reach a deal at crunch talks in Geneva on the weekend.
"We are not far from an agreement with the Iranians but we are not there yet." France foreign minister, Laurent Fabius, said.
Israel - key ally of the US in the region - and the US are locked in a bitter war of words over the negotiations to halt Iran's nuclear drive, suspected to be a front for developing a military capability.
"Our hope is that in the next months we can find an agreement that meets everyone's standards," Kerry said.
Israeli Prime Minister Benjamin Netanyahu has denounced the emerging agreement as "dangerous", while his defence minister, Moshe Yaalon, called it a "historical mistake."
Kerry insisted the United States has the interests of ally Israel at heart and that he shares Netanyahu's "deep concerns".
"But I believe the prime minister needs to recognise that no agreement has been reached about the endgame here, that's the subject of the negotiations," said Kerry.
Israel, the region's sole if undeclared nuclear power, views a nuclear Iran as an existential threat and has said it will not be "bound" by any world deal with Tehran, refusing to rule out the threat of military action to halt it.
The three-day long talks ended without an agreement, blamed by some media and off-the-record officials on French reservations on parts of a draft deal on the negotiating table.
Britain's Foreign Office, on Monday, appointed a veteran diplomat, Ajay Sharma, who was previously the deputy head of mission to Tehran as its non-resident charge d'affaires for Iran.
The British embassy was closed in late 2011 as tensions over a possible attack on Iran's nuclear facilities ran high.
The so-called P5+1 group and Iran will reconvene in Geneva on November 20 to try to iron out differences.
Negotiations over Iran's atomic activities had stalled for years, but the June election of Iranian President Hassan Rouhani -- seen as a relative moderate -- gave fresh momentum to the talks.