MONROVIA - The United Nations must resist pressure to cut back its mission in Liberia too soon, or risk instability before elections next year, its top official in the country said.

A big U.N. force has overseen the nation since the end of fighting in 2003 and cuts are being sought because of the operation's cost, U.N. Liberia mission chief Ellen Margrethe Loj said at the weekend.

But limitations of local funding and institutions must be taken into account and ethnic clashes were a threat to stability with potential consequences for all of West Africa, Loj said.

The U.N. Security Council will vote this week on a proposal to keep the 9,400 soldiers and policemen now in the country until elections are held at the end of next year, before re-assessing cuts to the mission.

The mission in Liberia costs $500 million a year to run, a figure that dwarfs the government's planned budget of $350 million for this year. Other donors provide three times as much again in aid projects.

Peacekeepers are still filling in for Liberia's army, which was scrapped at the end of the war and will not be operational again until U.S.-backed training is complete in 2012. The U.N. is also rebuilding the police force.