Earlier US President George W Bush said he hoped to resolve the nuclear dispute with Iran with diplomacy, but warned Tehran he would "use military might" if necessary to defend Israel.
The meeting, at Britain's UN mission, brought together US Under Secretary of State for Political Affairs Nicholas Burns, Russian Deputy Foreign Minister Sergei Kislyak and foreign ministry political directors John Sawers of Britain, Stanislas de Laboulaye of France, Zhang Yan of China and Michael Schaefer of Germany.
The gathering comes as the 15-member Security Council is reporting some headway in its bid to agree on the wording of a revised Franco-British draft.
It urges Iran to comply with International Atomic Energy Agency (IAEA) demands that the government in Tehran restore international confidence in its atomic program, which Iran insists is peaceful.
It also aims to reinforce the IAEA demands, including immediate suspension of all uranium enrichment activities and a return to a nuclear Non-Proliferation Treaty (NPT) protocol that allows for wider inspections of its nuclear facilities.
The six-nation meeting at the British UN mission is meant to take a broader and longer-term view of the nuclear standoff with Iran, particularly if Tehran refuses to comply with IAEA demands, diplomats said.
Warning to Iran
After a major speech defending the war in Iraq Mr Bush said that it was Iran’s stated objective to destroy Israel which he said was a threat to world peace.
"I made it clear, and I'll make it clear again, that we will use military might to protect our ally Israel," said Mr Bush, who was apparently referring to Iranian President Mahmoud Ahmadinejad's call for the destruction of Israel.
On the nuclear dispute, Bush said he hoped "to solve this issue diplomatically" with a "united message" to Tehran from Washington, London, Paris, Berlin as well as Russia "hopefully" and China.
The message would be that "your desire to having a nuclear weapon is unacceptable," he said.
Meanwhile at the IAEA headquarters in Vienna, diplomats said that Iran was about to run a 164-centrifuge cascade to enrich uranium, a step which they noted would heighten urgency for UN action on Tehran's nuclear program.
"Iran is on the verge of operating a 164-centrifuge cascade with UF6
(uranium hexafluoride gas)," a Western diplomat said.
Centrifuges arrayed in series, known as cascades, are used to produce fuel for nuclear power reactors or material for the explosive core of a nuclear weapon.