The five permanent members of the U.N. Security Council agreed Friday to move toward a third set of sanctions if Iran fails to answer key questions on its nuclear program, the British Foreign Office said.

The Foreign Office said the U.S., Russia, China, Britain and France agreed, along with Germany, to come up with a new sanctions resolution with the aim of voting on it if November reports by the European Union and the International Atomic Energy Agency did not show improved Iranian cooperation.

Russia and China did not comment, but the agreement would mark a surprising turnaround in the two countries' strong resistance to fresh sanctions against Iran.

IAEA head Mohamed ElBaradei will report to the U.N. on Iran's nuclear activities in mid-November. EU chief negotiator Javier Solana is also due to submit a report on Iran's cooperation.

The diplomats who met in London on Friday will hold talks again on Nov. 19 to assess the pending reports, a Foreign Office spokesman said.

He said that the Security Council members and Germany had agreed to "finalize a text for a third U.N. Security Council Sanctions resolution with the intention of bringing it to a vote in the U.N. Security Council unless the November reports of Dr. Solana and Dr. ElBaradei show a positive outcome of the efforts."

U.S. Undersecretary of State Nicholas Burns had urged China and Russia to support harsher U.N. sanctions, saying the two nations were key to a diplomatic solution to the standoff.

"The U.S. believes very strongly there is a need to accelerate the diplomacy, to strengthen the sanctions," Burns told The Associated Press.

"We want a diplomatic solution, we do not want to give up on diplomacy, but we need the help of the P5 (permanent Security Council member) countries to do that, particularly the support of Russia and China."

The U.S. and its allies accuse Iran of using a civilian power program as cover to develop nuclear weapons. Iran denies the charge and insists it needs the technology to generate power.

Britain and France have backed the U.S. call for a resolution on a third round of U.N. Security Council sanctions if Iran continues to refuse to suspend uranium enrichment.

Burns said the U.S. believes China has increased trade with Iran in the last six months, sending the wrong signal about the international community's attitude toward the nuclear program.

Iran's former president, Hashemi Rafsanjani, said Friday in Tehran that talks between Iran and the U.N. nuclear watchdog were making progress and he warned the U.S. to avoid resorting to threats.

"The U.S. is making mistakes. Iran is having talks (with the IAEA) and has said it will respond to IAEA questions. They are gradually coming and taking their response. One has to wait, talk and make discussions," he said.

Rafsanjani also spoke about the prospects of a U.S. attack against Iran, saying it would create a quagmire for Washington with unimaginable consequences.

Burns said participants at Friday's meeting did not discuss an offer from Saudi officials to create a Middle East consortium of users of enriched uranium.

The proposal by the Arab nations around the Persian Gulf is to build a uranium enrichment plant in a neutral country to supply the region's states, including Iran, with reactor fuel for nuclear energy programs.

Britain's Foreign Secretary David Miliband briefly discussed the proposal with Saudi Arabia's foreign minister, Prince Saud al-Faisal, during talks this week, a Foreign Office spokesman said.

Prince Saud told London's Middle East Economic Digest that the plan had been proposed to Iran's government, which said it would consider the proposal.

Burns said Washington would look carefully at the offer, but stressed a similar proposal from Russia — to host Iran's uranium enrichment facilities on its territory to allay Western concerns about monitoring — had been ignored.