But Britain and Germany get only about 1 percent of their oil from Iran, and France gets only about 3 percent from there. Other European countries, like Greece, Italy and Spain, are much more reliant on Iranian oil. Greece, for instance, gets about one-third of its oil from Iran, while Italy and Spain each get about 13 percent, according to European Union figures.

Greece, Italy and Spain were more reluctant than Britain, France and Germany to vote for rapid oil and banking sanctions against Iran.

Britain, France and Germany are also the European nations negotiating with Iran on its nuclear program in the talks that also include the United States, Russia and China and are presided over by the European Union’s policy chief, Catherine Ashton.

France and Britain have pushed hard to increase sanctions against Iran to get it to stop nuclear enrichment in what many in the West believe to be an Iranian program to build a nuclear weapon. The sanctions are part of a dual-track strategy that combines pressure with negotiations. Germany, however, has explicitly opposed any military action against Iran, while Britain and France, like the United States and Israel, have refused to rule out military action.

Iran denies that its nuclear program has any military intent, but it has flouted repeated Security Council resolutions requiring it to stop nuclear enrichment and cooperate fully with the International Atomic Energy Agency. Merging conciliation with threat, Iran has recently boasted that it was about to start a vast new array of centrifuges to enrich uranium deep in a mountain that would be very difficult to bomb, while it has renewed its call for negotiations after a gap of a year.

French officials believe the threat of new sanctions and the bite of older ones, together with the travails of the Syrian government and the hints of military action coming from Israel, are bringing Iran back to the table. They are concerned, however, that the Iranian offer for talks is simply another way to buy time while the centrifuges continue to turn. They also fear that if the talks fail, a military strike on Iran may follow.

Last week, Iran sent a letter to Ms. Ashton calling for a new round of negotiations with the group of six, in response to a letter from her on Oct. 17. The Iranian letter, from the country’s nuclear negotiator, Saeed Jalili, declared Iran’s “readiness for dialogue” at “the earliest possibility.” The letter, which was vague but did not contain preconditions, was greeted by Ms. Ashton and Secretary of State Hillary Rodham Clinton with a mixture of optimism and skepticism.