Britain's strategy for persuading Iran to give up its nuclear ambitions calls for sanctions that could be enforced militarily if diplomacy fails, but getting U.N. Security Council members Russia and China on board will be a struggle.

Britain, the United States, France and Germany are having trouble just getting China and Russia to agree on a Security Council statement calling on Iran to suspend uranium enrichment. Senior diplomats from the six countries met for 4 1/2 hours on Monday, apparently achieving little.

U.S. Ambassador John Bolton had expressed hope that the statement could be adopted after council discussions Tuesday afternoon. But after Monday's meeting, U.S. Undersecretary of State Nicholas Burns said more time was needed for negotiations.

"It may take a little bit of time, but it's going to be worth the time because when we do achieve that statement, it will be yet another clear unified message by the international community," Burns said.

The meeting, hosted by British Foreign Office Director John Sawers, occurred hours after a letter came to light detailing Britain's approach to Iran. The confidential document from Sawers laid out a scenario for getting Russia and China behind increasingly tough measures — including possible sanctions — to pressure Iran to abandon uranium enrichment. The process can be used to generate nuclear electricity or make nuclear weapons.

Britain's assessment was that the Iranians "will not feel under much pressure" from a Security Council statement alone "and they will need to know that more serious measures are likely," Sawers said.

The March 16 letter said measures could include a legally binding resolution that could be enforced by military means. But it acknowledged the challenge that negotiators will face in getting Russia and China onboard, and suggested a package of proposals to entice Iran.

"We are not going to bring the Russians and Chinese to accept significant sanctions over the coming months, certainly not without further efforts to bring the Iranians around," Sawers said.

The letter was addressed to Burns, German Foreign Office Political Director Michael Schaefer and French Foreign Ministry Political Director Stanislas de Laboulaye.

The immediate disagreement, with which the Security Council has grappled for a week, is over a proposed council statement urging Iran to abandon uranium enrichment and calling for a report in 14 days.

Moscow and Beijing want the International Atomic Energy Agency to assume the main role in cajoling Iran on uranium enrichment. They have warned that pushing Iran too hard could prompt its withdrawal from the Nuclear Nonproliferation Treaty and the expulsion of IAEA inspectors. They also contend that 14 days is too short for a progress report on Iran's compliance.

The six senior diplomats agreed on a brief statement expressing "deep concern" that Iran was continuing enrichment and had barred surprise IAEA inspections.

After the meeting, China's U.N. Ambassador Wang Guangya reiterated that Beijing could agree to Security Council action "if it is a short, brief political statement."

If there is no significant progress after 10 days, Western nations could abandon efforts to approve a Security Council statement in favor of a resolution that would be put to a vote, said a council diplomat who spoke on condition of anonymity because the issue had not been raised. A vote would force Russia and China to approve, abstain or veto action against Iran.

Negotiations between Iran and France, Germany and Britain collapsed in August after Tehran rejected incentives offered in return for a permanent end to enrichment. Its subsequent moves to toward enrichment capabilities led the IAEA to ask for Security Council involvement earlier this year.