The International Atomic Energy Agency is expected to condemn Iran for hiding its nuclear secrets and to warn Tehran it will not tolerate further violations of Iran's international obligations.
The IAEA board of governors reconvenes Wednesday to conclude a debate on Iran's nuclear program.
The United States now supports a draft resolution sponsored by key European countries that strongly criticizes two decades of deception by Iran in covering up its nuclear activities.
But the resolution falls short of declaring Iran in non-compliance with international obligations and makes no reference to sending the matter to the U.N. Security Council, something Washington originally pressed for.
But a senior Western diplomat, who did not want to be named, said the resolution "puts Iran on notice that the international community will not accept or tolerate repeated violations in the future".
If this occurred, the 35-member IAEA board would hold an emergency meeting to consider all possible options, including alerting the Security Council. The diplomat said the language was very clear and international pressure is still on Iran.
Diplomats say the draft resolution is likely to be adopted by consensus. The next stage is for the IAEA to carry out what it calls "robust verifications" at key Iranian nuclear facilities and conduct short notice inspections.
By February, the head of the IAEA, Mohamed ElBaradei, will draw up a report for the next board meeting scheduled for March.
Last week, Mr. ElBaradei told the board Iran was guilty of numerous failures and breaches of international nuclear obligations, but there was no evidence of a secret nuclear-weapons program as alleged by the United States.