Iran last night indicated it wanted to make significant changes to a draft agreement with the US and other world powers over its nuclear programme, in a move that may scupper the chances of any final accord being reached.

Almost two weeks after starting negotiations with the US, France and Russia over the draft, Iran finally delivered its response to the International Atomic Energy Agency in Vienna. The agency said last night it was negotiating with Iran and other parties over the accord, but western diplomats suggested Tehran's demands were unacceptable.