Iran should agree to freeze sensitive nuclear activity for at least a decade if it wants to strike a deal with the US, President Barack Obama has said.
However, the odds are against talks with Iran ending with an agreement, Obama told the Reuters news agency.
Negotiations on Iran’s nuclear programme are at a critical stage, with an outline agreement due on 31 March.
Israeli Prime Minister Benjamin Netanyahu is expected to urge the US Congress on Tuesday to oppose a deal.
He was invited to speak at the US Capitol by Republican House Speaker John Boehner, angering Democrats.
Netanyahu – who faces domestic elections in two weeks time – will not meet Obama during his visit to the US.
Interviewed at the White House, Obama moved to dial back tensions over Netanyahu’s planned speech, saying it was a distraction that would not be “permanently destructive” to US-Israeli ties.
But he strongly criticised Netanyahu’s stance and stressed there was a “substantial disagreement” between them over how to achieve their shared goal of preventing Israel’s arch foe from acquiring nuclear weapons.
Netanyahu had been wrong on Iran before when he opposed an interim nuclear agreement struck last year, Obama said.
“Netanyahu made all sorts of claims – this was going to be a terrible deal, this was going to result in Iran getting $50bn worth of relief, Iran would not abide by the agreement.”
None of that has come true, Obama said.
“During this period we’ve seen Iran not advance its programme. In many ways, it’s rolled back elements of its programme.”
US Secretary of State John Kerry is holding talks with Iranian Foreign Minister Zarif in Switzerland as part of the ongoing negotiations ahead of a 31 March deadline for a framework agreement.
The aim is then to secure a final deal by 30 June.
Obama said that if Iran was willing to agree to “double-digit years of keeping their programme where it is right now and, in fact, rolling back elements of it that currently exist… and we’ve got a way of verifying that, there’s no other steps we can take” to ensure Iran does not have nuclear arms.
Obama said that while a deal was still unlikely, it would be better than the alternatives.
“If they do agree to it, it would be far more effective in controlling their nuclear programme than any military action we could take, any military action Israel could take, and far more effective than sanctions will be,” the US president said.
The US goal is to make sure “there’s at least a year between us seeing them try to get a nuclear weapon and them actually being able to obtain one,” he said.
The Israelis say any agreement that leaves Iran with the potential to use a peaceful civilian nuclear programme for military means, now or in the future, is unacceptable.
“I have a moral obligation to speak up in the face of these dangers while there is still time to avert them,” Netanyahu told the American Israel Public Affairs Committee (AIPAC) conference in Washington on Monday.
Obama’s robust defence of a possible deal with Iran comes as his administration faces criticism from some quarters that it is being too eager to complete a deal, at the risk of allowing Iran to eventually become a nuclear state.