Officials from the permanent members of the UN Security Council plus Germany have held talks on Iran's nuclear programme without reaching agreement.
US official Nicholas Burns warned talks could take some time
Britain, France and the US are backing a draft statement calling for Iran to suspend nuclear activities.
The statement would require the UN's nuclear agency, the IAEA, to report back within weeks on Iran's compliance.
But China and Russia have expressed concern at the deadline and about the Security Council's role.
China and Russia are believed to be concerned that the Security Council's role in handling the issue of Iran's nuclear programme will overshadow the role of the International Atomic Energy Agency.
US Under-Secretary of State Nicholas Burns said the officials had made some progress, but had not agreed on the precise wording of a statement.
"It's clear from today's meeting that there has to be some more meetings up here in New York. [Agreement] may take a little bit of time," Mr Burns said.
Any statement that emerges from the Security Council has to have the agreement of all 15 council members.
The meeting was also meant to discuss longer-term strategy towards Iran if it does not comply, BBC New York correspondent Susannah Price says.
While the US, France and UK would then want to see a resolution calling on Iran to comply - with the possible threat of further measures if it does not - Russia and China oppose sanctions.