Washington: President Barack Obama has celebrated the "broad understanding" reached with Iran over its nuclear program and warned sceptics in his own Congress they would wear the blame should they seek to sabotage it.
"Today, the United States, together with our allies and partners, has reached a historic understanding with Iran, which, if fully implemented, will prevent it from obtaining a nuclear weapon," said the President in an address from the White House Rose Garden.
Though details still needed to be finalised and a deal signed, Mr Obama said the understanding shows a deal would "cut off every pathway that Iran could take to develop a nuclear weapon" would be enforced by the strictest inspection regime in ever negotiated and would increase the so-called "break out" time Iran needed to build a bomb should it chose to renege from a current two or three months to a year.
But his speech also recognised the bitter opposition to a deal with Iran being mounted by Republicans in Congress and by Israel.
"If Congress kills this deal not based on expert analysis, and without offering any reasonable alternative, then it's the United States that will be blamed for the failure of diplomacy. International unity will collapse, and the path to conflict will widen," he said, noting that polls show the American public backs a diplomatic response to the Iranian nuclear program.
"It's no secret that the Israeli prime minister and I don't agree about whether the United States should move forward with a peaceful resolution to the Iranian issue," he said. "If in fact Prime Minister Netanyahu is looking for the most effective way to ensure Iran doesn't get a nuclear weapon, this is the best option."
Speaking in Switzerland US Secretary of State John Kerry who has led the negotiations for the so-called P5+1 – permanent members of the Security Council as well as Germany – also dismissed those who opposed diplomatic efforts.
"Throughout history, diplomacy has been necessary to prevent wars and to define international boundaries, to design institutions and to develop global norms," he said. "Simply demanding that Iran capitulate makes a nice sound bite, but it's not a policy.
"The true measure of this understanding is not whether it meets all the desires of one side at the expense of the other. The test is whether or not it will leave the world safer or more secure than it would be without this agreement.
"And there can be no question that the comprehensive plan that we are moving toward will more than pass that test."
The Republican Speaker of the House, John Boehner, who controversially invited Benjamin Netanyahu to address Congress before the elections in Israel, stopped short of opposing the plan, but said his "immediate concern" was that the plan appeared to allow for the lifting of some sanctions against Iran.
"Congress must be allowed to fully review the details of any agreement before any sanctions are lifted," he said.
He added that his recent visit to the Middle East had confirmed his view that Iran's efforts to foment unrest and terrorism had grown.
"It would be naive to suggest the Iranian regime will not continue to use its nuclear program, and any economic relief, to further destabilise the region," he said
"In the weeks ahead, Republicans and Democrats in Congress will continue to press this administration on the details of these parameters and the tough questions that remain unanswered."
The Republican Senate Foreign Relations Committee Chairman Bob Corker of Tennessee, Bob Corker, said the US "must remain clear-eyed about Iran's history and its support for terrorism in the region."
Congressman Peter Roskam, an outspoken Republican supporter of Israel, said the deal, "promises the Iranian regime everything it wants" in return for "minimal promises from a dictatorial regime."
Earlier this year 47 Republican senators sought to derail the negotiations by signing a letter to Iranian leaders telling them that Congress could overturn any deal cut with the President after he left office next year.
Mr Netanyahu, tweeted that "any deal signed with Iran must significantly roll back Iran's nuclear capabilities and stop its terrorism and aggression," while Israel's Intelligence Minister Yuval Steinitz said the outline was "disconnected from the sad reality" of the region.
The nuclear expert Mark Fitzpatrick, director of the non-proliferation and disarmament program at the International Institute for Strategic Studies was positive about the framework agreement, describing it as "a win-win outcome for the world".
"We can't say it's a 'good deal', because there's no final agreement yet. But as a framework it's very good," he tweeted.
