Iran must commit to a verifiable freeze of at least 10 years on sensitive nuclear activity for a landmark atomic deal to be reached, but the odds are still against sealing a final agreement, US President Barack Obama said on Monday.

Interviewed at the White House, Obama moved to dial back tensions over Israeli Prime Minister Benjamin Netanyahu's planned speech to Congress on Tuesday opposing the Iran deal, saying it was a distraction that would not be "permanently destructive" to US Israeli ties.

But he strongly criticized 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.

Talks between major powers and Iran to restrict Tehran's nuclear capabilities in exchange for an easing of sanctions have reached a critical stage ahead of an end of March deadline for a framework deal and a June 30 date for a final agreement.

Obama's comment about the time frame for a freeze represents one of the US government's strongest signals yet of its red line for a successful deal.

"If, in fact, Iran is 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 ... if we've got that, and we've got a way of verifying that, there's no other steps we can take that would give us such assurance that they don't have a nuclear weapon," he 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," Obama said in the interview, carefully timed by the White House a day ahead of Netanyahu's polarizing speech to Congress.

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.

The White House last week denied a report that the United States and Iran were exploring a possible 10-year deal that would initially freeze Iran's nuclear programme but gradually allow it to increase activities that could enable it to produce nuclear arms in the last years of the agreement.

OBAMA: ODDS STILL AGAINST IRAN DEAL

In the interview, Obama again criticized a plan by Republicans and some Democrats in the US Senate to impose additional sanctions on Iran if no deal is reached by June 30, saying it could undermine the delicate talks.

"I'm less concerned, frankly, with Prime Minster Netanyahu's commentary than I'm with Congress taking actions that might undermine the talks before they're completed."

Despite recent progress in the talks, Obama suggested there had been little change in his assessment that the negotiations have less than a 50 percent chance of success.

"I would say that it is probably still more likely than not that Iran doesn't get to 'yes,' but I think that, in fairness to them, they have been serious negotiators and they've got their own politics inside of Iran. It is more likely that we could get a deal now than perhaps three or five months ago," he said.

An Iran nuclear deal would be a potential signature achievement for Obama whose foreign policy legacy is mixed with just two years left in office.

Seemingly intractable challenges, from Russian separatists in Ukraine to Islamic State militants in Syria, have overshadowed successes such as the killing of Osama bin Laden and the tentative opening up of relations with Cuba.

Israel fears that Obama's Iran diplomacy will still allow Iran to develop an atom bomb. Tehran denies it is seeking nuclear weapons.

Netanyahu has spoken scathingly about a possible deal, saying negotiators appear to have given up on a pledge to prevent Iran from acquiring nuclear weapons. He says a nuclear-armed Iran would pose an existential threat to the Jewish state.

NETANYAHU MADE "ALL SORTS OF CLAIMS"

US officials have said the "politicized" nature of Netanyahu's address, at the invitation of the Republican congressional leadership, threatens to undermine the close bilateral relationship.

In a speech on Monday to the American Israel Public Affairs Committee (AIPAC), the largest US pro-Israel lobby, Netanyahu again warned that a nuclear deal could threaten Israel's survival while insisting the US-Israeli relationship was "stronger than ever."

Obama said the rift with Netanyahu, with whom he has already had frosty ties, was not personal and that he would meet the Israeli leader again if he wins Israel's March 17 election. In a nod to Israeli concerns, he acknowledged that Iran's governmenthad a history of "anti-Israel and anti-Semitic statements."

But he reiterated the administration's criticism of Netanyahu's address and said the Israeli leader had been wrong before with his opposition to a 2013 interim deal with Iran.

"Netanyahu made all sorts of claims. This was going to be a terrible deal. This was going to result in Iran getting 50 billion dollars worth of relief. Iran would not abide by the agreement. None of that has come true.

"It has turned out that in fact, during this period we've seen Iran not advance its programme. In many ways, it's rolled back elements of its programme."

Israeli officials travelling with Netanyahu had no immediate comment.

Obama said that a key doubt was whether Iran would agree to rigorous inspection demands and the low levels of uranium enrichment capability they would have to maintain.

"But 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," Obama said.

Turning to ties with Asia's largest economy, Obama sharply criticized China's plans for new rules on US tech companies, urging Beijing to change the policy if it wants to do business with the United States and saying he had raised it with President Xi Jinping.

"This is something that I've raised directly with President Xi," Obama said. "We have made it very clear to them that this is something they are going to have to change if they are to do business with the United States."

On what could be another landmark foreign policy achievement, Obama said he hoped the United States will open an embassy in Cuba by the time of a Western Hemisphere summit in Panama in mid-April.

Washington and Havana announced on December 17 that they planned to restore diplomatic relations following 18 months of secret face-to-face talks. "There's a lot of work that still has to be done," Obama added.