The influential head of Iran's hardline parliament also repeated a warning that the regime could quit the nuclear Non-Proliferation Treaty (NPT) if it felt its "right" to have an atomic programme was being violated.

"The Islamic republic of Iran refuses to lose time and will in no way accept a suspension of enrichment," Gholam Ali Hadad-Adel was quoted as saying by Iranian news agencies.

"The Islamic republic's policy is not to leave the NPT," asserted the official, who is close to Iran's supreme leader Ayatollah Ali Khamenei.

"If our relationship with the IAEA (International Atomic Enegy Agency) is one of both obligations and rights, we will stay in the NPT. If that is not the case, staying in the NPT would be of no interest to us," he warned.

Iran insists it only wants to enrich uranium to make nuclear fuel, but the process can be extended to make weapons -- hence Western demands for a moratorium while a still-inconclusive IAEA probe is in progress.

The comments came as the United States, unable to win support for sanctions against Iran, gave its European allies "a couple of weeks" to draft a fresh approach to persuade Tehran to drop its disputed nuclear programme.

Russia and China, which both hold a veto on the UN Security Council, have made it clear they oppose coercive measures to rein in Iran's nuclear activities.

Diplomats said negotiators from the Security Council's five permanent members plus Germany planned to meet in London on May 19 to weigh a new package of incentives as well as penalties.