Yukiya Amano , director general of the International Atomic Energy Agency, addresses reporters on Capitol Hill on Aug. 5, 2015, after briefing members of the Senate Foreign Relations Committee about the nuclear accord with Iran. (Michael Mathes/AFP/Getty Images)

The head of the international organization that is the linchpin of the Iran nuclear deal told a Senate committee Wednesday that he cannot divulge confidential details of its arrangement to examine Iran’s nuclear research for any possible effort to develop a nuclear weapon.

Yukiya Amano, director general of the International Atomic Energy Agency, a United Nations-affiliated organization, spoke in private for more than an hour with members of the Senate Foreign Relations Committee.

Amano said most of the questions revolved around the issue of the IAEA’s arrangement with Iran to investigate that country’s ­declared and suspected nuclear facilities, and to probe work done more than a decade ago in what the United States thinks was preparation for developing nuclear weapons.

Confidentiality underpins the IAEA’s credibility, Amano said, and is provided to all countries that undergo IAEA inspections.

“There were many questions on this issue,” he said in an interview after he met with the committee. “I repeated that I am not authorized to share or discuss confidential information.

President Obama addressed the international deal to restrict Iran’s nuclear program at American University on Aug. 5, 2015. Here’s that full speech. (AP)

“If I don’t protect . . . confidentiality, no country will share information with us. We will be unable to implement the agreement. Confidentiality is an essential building block to protect the safeguard regime.”

Many opponents of the nuclear agreement with Iran have accused the IAEA of making a “secret deal” with Iran after a trip Amano made to Tehran last month while negotiations were still underway.

The announced purpose of the trip, widely reported at the time, was to ensure that the IAEA could visit facilities and talk with scientists so it can assess whether Iran tried to weaponize its nuclear program in the early 2000s. That is required before any sanctions can be lifted under the agreement reached last month in Vienna.

Congress is reviewing the deal, and in September will vote to approve or reject the agreement struck between Iran and six world powers.

Democrats and Republicans have asked to see the separate IAEA agreement.

Amano bristled at the term “secret deal” to describe the confidential agreement, but his explanation did not sit well with many committee members.

“Most members left here with greater concerns about the inspections regime than they came in with,” Sen. Bob Corker (R-Tenn.), the committee chairman, told reporters after the meeting. He called Amano a “fine man” who is laboring under limitations imposed by the “IAEA process.”

Here are key moments from President Obama’s speech at American University on Aug. 5, 2015, addressing the international deal to limit Iran’s nuclear program. Congress is reviewing the agreement. (AP)

Corker noted that Wendy Sherman, the lead negotiator for the United States in more than a year and a half of nuclear talks, has said she saw documents dealing with the side arrangement between Iran and the IAEA.

“My question is, if Wendy has been able to read it, why can’t we read it?” Corker asked.

Corker said he believes U.S. negotiators had “punted” and “given in” to Iranian demands, but he declined to declare himself firmly opposed to the agreement.

“You should put me in the very, very skeptical column,” he said.

Sen. Benjamin L. Cardin (Md.), the committee’s ranking Democrat, was disappointed by the lack of senatorial access.

“It doesn’t mean we have to see everything in the document, but I think there are provisions in the document that relate to the integrity of the review . . . that would be useful,” he said.

Amano said that the nuclear agreement with Iran would provide the IAEA the ability to investigate Iran’s nuclear program and determine whether its activities under the program are, in fact, all nonmilitary, as Iran claims.

He said that the agreement would cost about $9 million a year to implement and that the costs would include the expense of basing inspectors in Iran, ­installing high-tech monitoring equipment and conducting analysis at IAEA headquarters in Vienna.

Amano said the choice between implementing the agreement and rejecting it is clear.

“Either we have the most robust safeguard regime in the world, with reduced nuclear activities. Or we have the current, insufficient safeguard arrangement with more extensive nuclear activities,” he said. “From a verification point of view, implementation of the agreement is a clear net gain.”

Some senators suggested that there was little Amano could have said to influence them.

“This is not about convincing me,” said Sen. David Perdue (R-Ga.), one of 47 senators who signed an open letter to Iran’s leaders in March warning that an agreement might not outlast President Obama’s time in office. “I’ve already reached the conclusion that this does not prevent Iran from becoming a nuclear-weapons state.”