The United States rejected UN chief Kofi Annan's call that it hold direct talks on Iran's nuclear ambitions, saying Tehran was interested only in "delaying and stalling" resolution of the dispute.

United Nations Secretary General Kofi Annan addresses the Security Council at UN headquarters in New York during a meeting on the situation in Sudan, May 9. The United States rejected Annan's call that it hold direct talks on Iran's nuclear ambitions, saying Tehran was interested only in "delaying and stalling" resolution of the dispute. [AFP/File]

State Department spokesman Sean McCormack said Washington was comfortable backing European and Russian efforts to negotiate an end to Iran's suspected drive to develop nuclear weapons.

"We believe that we are following the right diplomatic process now," he said. "We have been in support of the EU-3, we have been in support of the Russian government in their direct negotiations with the Iranian government."

Annan told reporters in Vienna that as long as the Iranians felt the Europeans had to clear all decisions with the Americans, "I am not sure they will put everything on the table."

But McCormack said European offers of incentives and a Russian proposal to enrich uranium for the Iranians had failed so far because Tehran "has refused to engage in a constructive and serious manner.

"It engaged in a negotiating process that, by all outward appearances, would seem only to be an exercise in delaying and stalling while they continued on down the road of acquiring a nuclear weapon," he said.

Pressure for direct US-Iran talks has been mounting 26 years after the two countries broke diplomatic relations, but McCormack said the Americans did want to become the focus of the nuclear negotiations.

"The dynamic very quickly becomes one of which: Well, what is the United States going to do in terms of making concessions to satisfy the needs and desires of the other party across the table?" he said.

With a US push for UN sanctions against Iran stymied by opposition from Russia and China, Britain, France and Germany are working on a new diplomatic package of carrots and sticks.

EU-3 foreign ministers were due to discuss the package in Brussels on Monday and their political directors were to confer with their counterparts from the United States, Russia and China in London on Friday.

Officials said Nicholas Burns, US undersecretary of state for political affairs and number three in the State Department, would have a series of talks in London on Thursday ahead of the formal meeting.