U.N. Secretary-General Kofi Annan (search) warned U.S.-led coalition forces in Iraq that new military campaigns in Fallujah and other insurgent strongholds could jeopardize upcoming elections, according to a letter obtained Friday.

In the letter dated Oct. 31, Annan told American, British and Iraqi leaders that the United Nations wants to help prepare for the elections, scheduled for the end of January, but fears a rise in violence could disrupt the process.

"I have in mind not only the risk of increased insurgent violence, but also reports of major military offensives being planned by the multinational force in key localities such as Fallujah," Annan wrote in the letter, obtained by The Associated Press.

U.S. jets have launched multiple airstrikes against insurgent positions in Fallujah (search) and U.S. soldiers blocked roads leading to the city in preparation for a planned assault to put Fallujah and other insurgent bastions north and west of Baghdad under control of Iraq's interim government.

After meeting with European leaders at a European Union summit in Brussels, Iraq's interim Prime Minister Ayad Allawi (search) said Friday the window for a peaceful settlement of the standoff over Fallujah was closing fast. A Fallujah offensive would involve a combination of U.S. and Iraqi forces.

Annan warned that major military assaults, "in which the main burden seems bound to be borne by American forces," may discourage Iraqis from participating in the vote.

Annan urged the coalition to give more time for dialogue to succeed and offered U.N. help.

"I, and all my colleagues at the United Nations Secretariat, want to help," Annan wrote. "But we need a conducive environment if elections are to produce a positive effect."

Given that Allawi's latest comments came a week after Annan's letter was sent, it appeared that Iraqi and American leaders were not seriously considering the offer.