Vienna  - The United States on Tuesday granted inspectors of the International Atomic Energy Agency (IAEA) greater access to its civilian nuclear programme and expressed hope that more countries would adopt the stricter monitoring regime.

The IAEA, the United States and other countries have been pushing Iran to implement the so-called Additional Protocol, as it would have given the IAEA greater powers in probing the country's alleged military nuclear projects.

US Ambassador Gregory Schulte handed over his country's ratification of the Additional Protocol to the IAEA in Vienna on Tuesday.

"We hope that our step will encourage other states to adopt and implement the Additional Protocol," Schulte said in a statement.

The stricter regime gives IAEA inspectors access to a wider range of nuclear-related sites, such as research laboratories and uranium mines. It also allows for short-notice inspections.

As of late November, 88 of the 128 IAEA member states had adopted the stricter guidelines. Nuclear weapons holders Israel, India and Pakistan have not yet done so.

With the US accession, all five nuclear weapons states that are members of the Nuclear Non-Proliferation Treaty - China, Britain, France, Russia and the US - now have the standard in place.

IAEA inspectors are stilled blocked from monitoring military- related sites under the protocol.

The move by the United States was a signal to Iran, an official close to the IAEA said. "It's more a symbolic step," he said. (dpa)