US warns Iran of more 'isolation' in nuclear dispute

The United States warned Iran that it faces further international isolation if it fails to address the UN nuclear watchdog's concerns about its atomic activities, which the West suspects may have military purposes.

The European Union also used a board meeting of the UN's International Atomic Energy Agency to pile pressure on Iran to stop obstructing an IAEA investigation into suspected atom bomb research by Tehran, which denies the charge.

Washington and its Western allies were signalling their determination that the Islamic state must give the IAEA access to sites and documents, regardless of broader talks between Iran and world powers that resumed last week.

Iran's envoy to the Vienna-based UN agency hit back, saying the allegations over his country's nuclear work were "baseless" and suggested the IAEA, not Tehran, was to blame for the failure so far to revive the stalled inquiry.

Some diplomats say Iran is using its meetings with the IAEA merely for leverage in negotiations with world powers which, unlike the UN agency, have the power to ease sanctions that they have recently tightened on the major oil producer.

US envoy Joseph Macmanus accused Iran of "provocative actions", particularly the installation of advanced centrifuges that would enable it to speed up its uranium enrichment.

"We are deeply concerned with what appears to be Iran's unwavering commitment to deception, defiance, and delay," Macmanus told the IAEA's board of governors.

Western countries fear Iran is enriching uranium to develop the capacity to build nuclear weapons and have imposed several rounds of sanctions. Iran says the programme is legitimate and intended for purely peaceful purposes.

Israel says Tehran is secretly trying to develop a nuclear weapon and has threatened pre-emptive strikes if it deems diplomacy ultimately futile.

The Vienna-based IAEA has been trying for more than a year to persuade Iran to give it the access it says it needs for its investigation, so far without progress.