Allawi's diplomatic rebuke was in response to Annan's letter late last week warning the leaders of the United States, Britain and Iraq that an all-out assault on Fallujah could undermine national elections set for January and further alienate Iraqis.

Early Monday, U.S.-led coalition and Iraqi forces launched a long-awaited offensive against Fallujah after Allawi gave the green light. The invasion is aimed at wresting control from insurgents and re-establishing government control of the Sunni Muslim city before elections.

Iraq's U.N. Ambassador Samir Sumaidaie asked to meet Annan on Monday afternoon and told reporters afterward that attacking Fallujah was "the least damaging, the least dangerous" option to restore law and order to the city, which is now under "a Taliban-like rule."

He said Annan "shares our abhorrence at the terrorists and their actions" and "I think the secretary-general accepts that this is an Iraqi matter, and a decision must be taken by the Iraqi government."

In his three-page letter, Allawi told Annan he could not give violent extremists a veto over Iraq's democracy or let them "continue to terrorize the vast majority of Iraqis who want to live in peace and freedom." He said the extremists had time enough to join the political process.