The UN atomic watchdog chief sought Tuesday to ease concerns in the United States about its investigation into Iran's alleged past nuclear activities following July's landmark deal with major powers.

"The arrangements made with Iran are technically sound and consistent with IAEA safeguards practices. They do not compromise our standards in any way," International Atomic Energy Agency chief Yukiya Amano said at a meeting in Vienna.

Under the July 14 agreement aimed at ending a 13-year standoff, Iran will dramatically reduce in scale its nuclear activities in order to make any dash to produce atomic weapons all but impossible.

It will be up to the IAEA, which already has up to 10 inspectors in Iran every day, to verify that Iran sticks to its commitments and does not divert material to any covert nuclear weapons drive.

This will require additional material and personnel, and Amano on Monday called on member states to provide an additional 9.2 million euros ($10.6 million) in annual funding.

But the July deal is not just about Iran's present and future activities, it is also about what the Islamic Republic may have done in the past.

The IAEA also wants to investigate allegations that at least until 2003 Iran conducted research into developing nuclear weapons. Tehran denies this.

On the same day as Iran's deal with the six powers, it also signed with the IAEA a separate "road map" deal aimed at closing for good the thorny "possible military dimensions" file by the end of the year.

Iran provided to the IAEA on August 15 "explanations in writing, and related documents" which the watchdog will review by September 15. Follow-up meetings and inspections have to be done by October 15 and Amano will issue a final report by December 15.

However, details of how this investigation will work, as well as a separate agreement regarding the Parchin military base where explosives testing allegedly took place, are confidential.

This has raised concerns among opponents to the main deal with Iran -- which US lawmakers still have to approve -- that Iran will hoodwink the IAEA.

This might include the IAEA still not having access to sites such as Parchin, relying instead on the Iranians to provide soil samples and imagery.

US Republican presidential hopeful Jeb Bush, denouncing the wider Iran deal as "a farce", said last week that "inspections of state sponsors of terrorism can't work on the honour system".

Iran's ambassador to the IAEA, Reza Najafi, on Tuesday refused to be drawn on providing more details of the investigation, including on Parchin.

"We have some procedures, some arrangements (with the IAEA), which are confidential. I cannot disclose those arrangements. This is not only the commitment of Iran, it is also the commitment of the agency. We cannot discuss the details of any arrangement whatsoever," Najafi told reporters.

"I am not responsible for what happens in Washington."