British Foreign Secretary William Hague has said that Iran is clearly trying to develop a nuclear weapons capability.

Speaking in an interview in today’s Daily Telegraph, Mr Hague said that if Iran succeeds it will set off a dangerous round of nuclear proliferation across the Middle East.

Iran says its uranium enrichment programme is purely for civilian purposes, but Western powers suspect Tehran is trying to develop the ability to produce nuclear weapons.

Western powers have been pressing Iran to hold substantive talks on its nuclear programme and want it to halt its uranium enrichment, but Iran says it has an absolute right to press ahead with its plans.

Several rounds of increasingly punitive United Nations and Western sanctions have failed to persuade Iran to stop its enrichment programme, some of which has been moved to underground buildings for greater security.

The Iranians "are clearly continuing their nuclear weapons programme," Mr Hague told the newspaper.

He added: "If they obtain nuclear weapons capability, I think other nations across the Middle East will want to develop nuclear weapons.

"The most serious round of nuclear proliferation since nuclear weapons were invented would have begun, with all the destabilising effects in the Middle East, and the threat of a new Cold War in the Middle East without necessarily all the safety mechanisms. That would be a disaster in world affairs."

There has been public discussion in Israel about whether it should attack Iran to stop it from developing a nuclear bomb.

Tension between the two countries has been raised by attacks on Israeli diplomats abroad and the recent killing of an Iranian nuclear scientist in Tehran.

"We are very clear to all concerned that we are not advocating military action," Mr Hague said.

"We support a twin-track strategy of sanctions and pressure, and negotiations on the other hand. We are not favouring the idea of anybody attacking Iran at the moment."

The latest signal from Tehran that it might be willing to resume talks on the nuclear issue, in the form of a letter to European Union foreign policy chief Catherine Ashton, has been greeted with cautious optimism by the US and the EU.

Elsewhere, Israeli Defence Minister Ehud Barak has said that a nuclear-armed Iran would trigger an arms race in the Middle East and nations should impose "crippling" sanctions on Tehran to force it to give up its atomic programme.

Barak said despite Western sanctions inflicting increasing damage on Iran's oil-based economy he had not seen any sign that Tehran was ready to give up its nuclear ambitions.