The White House on Wednesday insisted it had confidence in the International Atomic Energy Agency, after it emerged that the watchdog may allow Iran to self-inspect some suspected nuclear sites.

The White House stressed that a purported deal between the IAEA and Tehran was separate from the soon-to-begin inspection regime agreed by global powers and Tehran.

National Security Council spokesman Ned Price said the confidential IAEA-Iran agreement was "unique to the agency's investigation of Iran's historical activities."

The possible military dimensions of Iran's past program was a major stumbling block during the talks with Iran that resulted in a comprehensive nuclear deal.

In that deal, Iran must provide a full accounting of past nuclear activity before an initial batch of sanctions are lifted.

But in a concession, the international community agreed that the IAEA would judge whether Iran complies.

"We are confident in the agency's technical plans for investigating the possible military dimensions of Iran's former program, issues that in some cases date back more than a decade," said Price.

"When it comes to monitoring Iran's behavior going forward, the IAEA has separately developed the most robust inspection regime ever peacefully negotiated to ensure Iran's current program remains exclusively peaceful," he added.

The Associated Press had earlier reported the IAEA would allow Iran to provide its own experts to inspect sites like Parchin, the sprawling, particularly sensitive complex near Tehran.

Owned by the Defense Industries Organization, the complex is effectively run by Iran's hardline Islamic Revolutionary Guards.

The IAEA suspects Parchin was used for high explosive and hydrodynamic tests linked to the development of nuclear weapons.

Reports on the details of the IAEA investigation prompted immediate condemnation Wednesday from critics of the broader multilateral deal.

The "Iran deal is a farce," said Republican presidential candidate Jeb Bush. "Nuclear inspections of state sponsors of terrorism can't work on the honor system."

Iran has already handed over documents linked to its previous nuclear activity, but it has also been accused of cleaning up Parchin.

The well-respected Institute for Science and International Security in August questioned Iran's claims that this work was construction work near an off-site dam.