Further steps could include a referral of Iran's to the UN Security Council for measures ranging from a warning to sanctions.
Today's meeting was called following Iran's resumption of activities at its Natanz uranium-enrichment facility on 10 January.
Iran's renewal of work at the plant raised alarms because it suggests Iran will continue to try to master the process of uranium enrichment. Enriched uranium can be used as fuel for nuclear reactors and, at high levels of enrichment, as material for making nuclear bombs.
France, Britain, and Germany -- the so-called EU-3 -- say talks with Iran aimed at convincing Tehran to voluntarily give up uranium enrichment efforts have reached a dead end.
The Europeans have called for an emergency meeting of the International Atomic Energy Agency (IAEA) to discuss the transfer of Iran's nuclear dossier to the UN Security Council. Their decision is backed by the United States.
"I am not going to prejudge what the United Nations Security Council should do," U.S. President George W. Bush said on 13 January at a news conference at the White House with German Chancellor Angela Merkel. "But I recognize that it is logical that a country [Iran] which has rejected diplomatic entreaties be sent to the United Nations Security Council."
Russia and China have so far opposed any move to refer Iran to the UN body. But since Iran's resumption of activities related to uranium enrichment in early January, Russia has become increasingly critical of the Islamic Republic, leading to speculation that it could change its position.
China has also criticized Tehran for resuming uranium-enrichment-related activities, but the Chinese Foreign Ministry said recently that the issue should be resolved within the IAEA.
Despite the increasing international pressure, including today's meeting in London, Iranian officials remain defiant and say the resumption of nuclear research is "irreversible."
"We do not consider [research and development] activities [to be] nuclear-fuel production, and asking to stop research means asking to close the universities, asking [us] not to realize and find out in the field of science, and research is the blood of science in any area, in all the areas. And how can we accept to stop?" Foreign Minister Manuchehr Mottaki said in an interview with Reuters on 15 January.
Tehran says its nuclear program is solely aimed at peaceful purposes, but Washington accuses Iran of secretly developing nuclear weapons.
IAEA Director-General Mohammad el-Baradei is quoted as saying in an interview printed in the 23 January issue of the U.S. weekly magazine "Newsweek" that he could not exclude the possibility that Iran might have a secret nuclear-weapon program distinct from activities known to his agency.
"If they have the nuclear material and they have a parallel weaponization program along the way, they are really not very far -- a few months -- from a weapon," el-Baradei told "Newsweek."
Israeli officials have suggested Iran could get the bomb by 2007. Many U.S. experts say Tehran would need at least five years to develop a weapon.