The diplomatic row between Iran and the United Nations Security Council intensified on Saturday when Iranian envoy Ali Asghar Soltanieh told the IAEA that the agency had not provided genuine documents to back up fresh accusations about Iran's nuclear program, and that the matter was "closed".

The accusations are based on Western intelligence reports suggesting that the Tehran government secretly combined uranium processing, airborne high-explosive tests and work to remodel a missile cone in a way that would fit a nuclear warhead.

"The government of the United States has not handed over original documents to the agency since it does not in fact have any authenticated document and all it has are forged documents," Soltanieh wrote in a letter to IAEA chief Mohamed ElBaradei. "The alleged studies are politically motivated and baseless allegations."

West shows united front in Frankfurt

At a meeting held near Frankfurt this week, Germany joined the five members of the UN Security Council in calling on Iran to negotiate with the UN about its nuclear program. Germany, France, Britain and the United States have also threatened Iran with a fourth round of sanctions if it continues enriching uranium and refuses to resolve concerns.

German Foreign Minister Frank-Walter Steinmeier aligned himself with its UN allies in an interview in Saturday's Hamburger Abendblatt newspaper. "At the moment, I am sceptical. If the situation stays as it is, we will have to enter a new round of sanctions. We will have to increase the pressure."

Despite the latest spat, Steinmeier said he remained optimistic that Iran's alleged nuclear weapons program could still be stopped.

The European Union also leant its weight to the growing Western pressure on Iran at a meeting of European foreign ministers in Stockholm this week. Iran is currently refusing to bow to all demands, and has stated that it will only speak to the IAEA.

IAEA urges Iran to clear up questions

While the IAEA has admitted that it does not have proof of an Iranian weapons plan, it urged Iran to clear up questions rather than dismiss intelligence reports as forgeries. According IAEA, Tehran is not cooperating sufficiently with its enquiries, and has consistently denied the agency access to sites.

US State Department spokesman Ian Kelly told reporters, "We have provided a path whereby Iran can become a full and respected member of the international community. It is up to Iran to make a decision as to whether it chooses that path."

A US official who wished to remain anonymous also stated that Soltanieh's accusation of forgery was baseless.

The new exchange of accusations follows a week of mixed signals from the Iranian government, whose chief nuclear negotiator Saeed Jalili issued a statement saying Iran was ready to talk to world powers about an updated nuclear proposal for the country. On Thursday, after both the USA and the EU claimed they had not received any official notification of such a proposal, Foreign Ministry spokesman Hassan Ghashghavi declared that Iran would only speak to the IAEA.

bk/Reuters/dpa

Editor: Nick Amies