The discussions at Britain's UN mission on Monday were intended to map out a long-term strategy on the Iran nuclear crisis.
The meeting brought together Nicholas Burns, the US under-secretary of state for political affairs, Sergei Kislyak, the Russian deputy foreign minister, 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 attempt to agree a revised Franco-British draft urging Iran to comply with International Atomic Energy Agency (IAEA) demands that Tehran restore international confidence in its atomic programme, which Iran insists is peaceful.
The text 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.
Iran insists its atomic programme
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.
Meanwhile at the IAEA headquarters in Vienna, diplomats said on Monday 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 programme.
"Iran is on the verge of operating a 164-centrifuge cascade with UF6 [uranium hexafluoride gas]," a Western diplomat said, referring to machines arrayed in series, known as cascades, used to produce fuel for nuclear power reactors or material for the core of an atom bomb.