As Iran and six world powers led by the US reached a historic accord to curb Tehran's nuclear programme, President Barack Obama vowed to fight for it in a hostile Republican-controlled Congress.
"This deal is not built on trust," he said of the agreement between Iran and P5+1 - Britain, China, France, Russia and the US plus Germany after marathon talks in the Austrian capital of Vienna Tuesday.
"It is built on verification," Obama said from the East Room of the White House in an early morning appearance with Vice President Joe Biden by his side.
Asserting that the agreement would deny Tehran a pathway to nuclear weapons and require international inspections for compliance, Obama also vowed to veto any congressional attempt to scuttle the agreement.
"I believe it would be irresponsible to walk away from this deal," he said. "I will veto any legislation that prevents the successful implementation of this deal."
Obama asserted that his successors in the White House "will be in a far stronger position" to restrain Iran for decades to come than they would be without it.
Obama is expected to make calls to world leaders during the day.
The agreement met the goals he had in place throughout negotiations, said Obama praising the deal.
"Today after two years of negotiation the United States together with the international community has achieved something that decades of animosity has not: a comprehensive long-term deal with Iran that will prevent it from obtaining a nuclear weapon," he said.
The accord is expected to face fierce opposition from Republicans in the US Congress, as well as from Israeli Prime Minister Benjamin Netanyahu, a longstanding critic of the negotiations.
"From the initial reports we can already conclude that this agreement is a historic mistake for the world," Netanyahu was quoted as saying in a CNN report.
"Far-reaching concessions have been made in all areas that were supposed to prevent Iran from obtaining nuclear weapons capability."
US Congress has 60 days to review the agreement, giving its opponents plenty of time to dig into the details and challenge the Obama administration's position.
US Secretary of State John Kerry also praised the Iran nuclear deal saying from Vienna that the agreement is a step toward peace and a step away from conflict.
"This is the good deal that we have sought," Kerry said at a press conference, adding that "contrary to the assertions of some," this deal has "no sunset".
(Arun Kumar can be contacted at arun.kumar@ians.in)
