The three European nations that won Iran's consent to suspend uranium enrichment have drawn up a resolution to maintain pressure on Tehran.
Iran denies claims that it wants to build nuclear weapons
Iran said on Monday it was halting work on enrichment in a move hailed by the United Nations' nuclear watchdog, the International Atomic Energy Agency.
The IAEA board is scheduled to discuss Iran's compliance on 25 November.
Diplomats who have seen the motion drawn up by France, Britain and Germany say it is unlikely to satisfy the US.
The US has led calls for the IAEA to refer Iran to the UN Security Council, which has the power to impose sanctions.
The European nations' draft resolution calls on Iran to "sustain the suspension" of uranium enrichment at nuclear facilities in the cities of Isfahan and Natanz.
It proposes that the head of the IAEA should "report immediately" to the agency's board if there is any evidence of incomplete suspension".
The US is thought to prefer a tougher stance, whereby any lapse would immediately trigger Iran's referral to the UN Security Council.
"For the US, there's a lot of negotiating left to go," AFP news agency quoted one diplomat as saying.
Another, who also did not wish to be named, said "much work" remained to be done on the draft resolution but expressed confidence that a solution would be reached.
The IAEA is now checking "to see that everything has been stopped", the watchdog's director general Mohamed ElBaradei said.
He will deliver his verdict on Iran's conduct when the agency's 35-member board meets on Thursday.
Mr ElBaradei welcomed news of Iran's suspension as "a good step in the right direction" that could "build confidence" in the Iranian government's intentions.
He also said that Iran had made the uranium gas used in enrichment but that the quantities involved were not enough to produce a nuclear weapon.
Iran reacted angrily to recent reports that it was speeding up uranium enrichment during the week-long gap between the deal being struck and the deadline for its introduction.
Tehran also hit back at outgoing US Secretary of State Colin Powell's assertion that it was trying to adapt its ballistic missiles to carry nuclear warheads.
"I believe Powell has understood his remarks were false," Iran's nuclear chief Hassan Rohani told state television on Sunday. "Such claims are totally baseless."
But Mr Powell has refused to back down, telling reporters on a flight to the Middle East: "I stick with it."
Iran has always denied US claims that it is developing a nuclear weapons programme, saying its intentions are peaceful.
UK Foreign Secretary Jack Straw told reporters in Brussels that Iran's move was a positive one but warned that it was not the end of the matter.
"If there is a failure by Iran to meet its obligations then Britain and also Germany and France reserve our collective right to refer the matter to the Security Council," Mr Straw said.
Sanctions remain unlikely as China and Russia, two of the five permanent members of the UN Security Council, have said they support Iran's stance.