TEHERAN (AFP) - Iran has quit nuclear talks with the major powers, accusing Washington on Friday of going against the spirit of a landmark agreement reached last month by expanding its sanctions blacklist.

A spokesman for EU foreign policy chief Catherine Ashton, who represents the powers in the talks, said both sides had headed home for consultations and that she expected the talks to resume soon.

But Iran's chief nuclear negotiator Abbas Araqchi said the US move went against the spirit of the deal struck in Geneva under which the powers undertook to impose no further sanctions for six months and Teheran was weighing the "appropriate response".

"America's move is against the spirit of the Geneva deal," Araqchi told the Fars news agency as his team headed back to Teheran from Vienna.

"We are evaluating the situation and will make the appropriate response," he said.

Under the deal, Iran agreed to freeze parts of its suspect nuclear programme for six months in return for some US$7 billion (S$8.8 billion) in relief from Western sanctions as it negotiates a final, comprehensive accord to allay suspicions it seeks a weapons capability.

Iranian negotiators quit the implementation talks late on their fourth day on Thursday after Washington blacklisted a dozen companies and individuals for evading US sanctions.

Mehr news agency quoted informed sources as saying the "new American sanctions" were the reason for the interruption.

"The negotiations were halted by Iranian delegation because of new American sanctions. The Iranian negotiating team has halted the talks at this stage and are headed back to the capital due to America's lack of commitment to the agreement," Mehr reported.

But a spokesman for the EU foreign policy chief said both sides needed to return home for consultations and that Iran's move was not unilateral.