"The US' goal is to pass a strong resolution that will support the IAEA's efforts to get to the bottom of Iran's nuclear programme," ambassador Kenneth Brill told AFP.
Brill said the hoped-for resolution should "stress the urgency of Iran cooperating fully with the IAEA, which it has yet to do."
Washington accuses Tehran of using its nuclear energy programme as a front to develop nuclear arms, and the recent discovery of enriched uranium at a nuclear site in Iran has heightened Western concerns over the Islamic regime's agenda.
Brill said the IAEA's latest two reports on Iran confirms that it was flouting the nuclear Non-Proliferation Treaty by failing to declare vital information about its atomic programme.
"Iran's pattern of behaviour is exactly what one would expect of a state seeking to violate the NPT and acquire a nuclear weapons capability," he said.
But he stopped short of saying that Washington and its allies on the IAEA's 35-member board of governors would push for a resolution calling it in non-compliance with the treaty.
Such a resolution could send the matter to the UN Security Council, which could in turn impose tough sanctions on the Islamic republic.
Western diplomats said the US was lobbying behind the scenes ahead of the start of the IAEA meeting on Monday, but knew it would not get the vote of board members from the non-aligned world for such a measure.
"The tradition at the board is to seek consensus as far as possible. They will not get a resolution to refer the matter to the Security Council," one source told AFP.
Another diplomat said the United States did not wish "to take the matter out of Vienna", the headquarters of the IAEA, because it believed the UN watchdog was the best forum in which to deal with Iran.
The IAEA, the United States and the European Union are urging Iran to sign and implement an additional protocol to the Non-Proliferation Treaty which would allow surprise inspections of its nuclear sites.
But deputy Iranian president Mohammad Ali Abtahi said Wednesday that Tehran had not yet decided whether to sign the protocol and the matter was "still under consideration."
The IAEA has since June carried out five inspection trips to Iran and August 26 released a report to the board of governors containing some of its findings.
While the report is understood to give no proof that Iran is pursuing a weapons programme, diplomats say it shows that Iran tried to sanitise one site before allowing inspectors in.