Britain says Iranian threats to resume uranium enrichment undermine earlier assurances that Iran would curb its nuclear program.
The issue of Iran's nuclear program arose as European foreign ministers met in Brussels. Britain, France, and Germany have lead European Union diplomatic efforts on the Iranian nuclear dispute.
Going into the Brussels meeting, British Foreign Secretary Jack Straw told reporters pressure must be maintained on Iran to fulfill its promise to use nuclear power only for peaceful civilian purposes.
"Since we got together - France, Germany and ourselves - 15 months ago, we have worked extremely hard to try to resolve this issue in a straight-forward way," he said. "It does, however, require the Iranians to meet their commitments for a full suspension of their uranium enrichment activity."
Mr. Straw said Tehran promised last October to suspend all uranium enrichment programs. But now Iran says it will partially resume the enrichment process, raising fears it wants to develop a nuclear weapon.
Mr. Straw said Iran's position undermines confidence within the international community about Iran's intentions.
Britain, France, and Germany have drafted a resolution for consideration by the U.N. nuclear regulatory agency that would set a November deadline for Iran to answer concerns about its nuclear program.
The United States favors putting Iran on notice that it could face U.N. Security Council sanctions if it does not cooperate.