Iran's refusal to budge on its objections to the agenda of a nuclear conference pushed the meeting closer to collapse Thursday, as diplomats said Tehran had set up hundreds more centrifuge machines to enrich uranium at an underground facility.

Iran has said it is determined to expand its disputed nuclear programme and further defy UN demands that it freeze all prepara-

tions for enrichment, a potential pathway to nuclear arms.

Diplomats familiar with Iran's nuclear programme said Tehran had recently set up more centrifuges at its underground uranium enrichment plant at Natanz, bringing the number of machines ready to spin uranium gas into enriched form to more than 1,600.

The diplomats spoke on condition of anonymity because they were not authorised to comment on internal conference matters to the media.