WASHINGTON (AP) -- Giving a scientific defense of the emerging nuclear deal with Iran, Energy Secretary Ernest Moniz called the plan a "forever agreement" that would block all pathways to a nuclear weapon and set up tough international inspections with no end date.

Moniz, a nuclear physicist, spoke at the White House on Monday as the Obama administration ramped up its campaign for a framework deal with Iran that has drawn criticism from congressional Republicans, the Israeli government and skeptical Arab allies of the U.S.

Under the agreement, Moniz said, all plutonium created as a byproduct of Iran's nuclear power production would be sent out of the country so it couldn't be used to make weapons. And international inspectors would watch over all stages of Iran's nuclear program to ensure Tehran sticks to the agreement.

"This is not built upon trust, this is built upon hard-nosed requirements," Moniz said, describing the deal as providing "unprecedented access and transparency" to Iran's nuclear program.

The White House says the tougher inspection requirements would continue in perpetuity.

"It's not a fixed-year agreement," Moniz said. "It's a forever agreement, in a certain sense, with different stages."

Many Congress members, including several Democrats, have worried that the final deal may lift sanctions on Iran without ensuring that Tehran keeps its word.

At the same time, skeptical Arab allies worry about Iran's destabilizing activity in the region. President Barack Obama has invited leaders of six Gulf nations to Washington this spring and said he wanted to "formalize" U.S. assistance.

Obama is staunchly defending the framework agreement worked out with other world powers as a "once-in-a-lifetime opportunity" to prevent an Iranian bomb and bring longer-term stability to the Middle East. He insists the U.S. would stand by Israel if it were to come under attack, but acknowledged that his pursuit of diplomacy with Tehran has caused strain with the close ally.

"It's been a hard period," Obama said in an interview with New York Times columnist Thomas Friedman. He added that it is "personally difficult" for him to hear his administration accused of not looking out for Israel's interests.

"We are powerful enough to be able to test these propositions without putting ourselves at risk," he said, citing his overtures to Cuba and Myanmar as other examples of his approach.

The framework reached with Iran last week clears the way for negotiators to hammer out technical details ahead of a June 30 deadline for a final deal.

Obama argued that successful negotiations presented the most effective way to keep Iran from obtaining a nuclear weapon, but insisted he would keep all options on the table if Tehran were to violate the terms.

"I've been very clear that Iran will not get a nuclear weapon on my watch, and I think they should understand that we mean it," Obama said in the interview published Sunday.

The president said there are many details that still need to be worked out with the Iranians and cautioned that there would be "real political difficulties" in implementing an agreement in both countries. He reiterated his opposition to legislation that would give the U.S. Congress final say in approving or rejecting a deal, but said he hoped to find a path to allow Congress to "express itself."