The UN's nuclear inspections chief rejected claims by U.S. President Donald Trump and other administration officials that his agency's enforcement of the Iran nuclear deal has been "weak."

"Some people believe that our verification activities are weak. This is not true," said International Atomic Energy Agency Director-General Yukiya Amano, on a visit to Washington on November 7.

"We have had access to all the locations that we needed to visit, and this should continue," he said, adding that inspectors have been able to turn up at Iranian sites with as little as two hours' notice and were given access in more than 90 percent of cases.

The 2015 nuclear agreement gave Iran sanctions relief in exchange for curbs on its nuclear activities which are verified by the UN agency.

Trump cited "weak inspections" last month as a reason for not certifying that Iran was complying with the deal.

But Amano said U.S. concerns have been "exaggerated." He said that in particular, whether a site is military or civilian is not "relevant," as some U.S. officials say.

"The places that interest us are the places that have nuclear material, nuclear expertise, and nuclear-related equipment," he said.

Amano visited Iran last week and met with President Hassan Rohani and other top officials. He said all assured him that Tehran would not be the first to pull out of the deal.

A key factor enabling the UN watchdog to inspect facilities in Iran has been Iran's provisional implemention of an international protocol that gives the agency more tools to verify compliance, Amano said.

It would be "a pity" if Iran were to stop allowing the agency to use those tools, he said, suggesting that pressure from the United States over the nuclear deal might prompt Tehran to backtrack at some point.

Based on reporting by AFP and Reuters