By Patrick Worsnip

UNITED NATIONS, Sept 4 (Reuters) - The U.N. Security Council parried on Thursday a request from Somalia to send a peace-keeping force to the violence-torn nation, saying it would consider doing so when conditions there had improved.

But in an official statement, the 15-nation council asked U.N. Secretary-General Ban Ki-moon to step up contingency planning for such a force and approach states to seek troop offers. It requested him to report back in 60 days.

The council was responding to an appeal from Somalia's interim government and an opposition faction with which it signed a peace agreement last month to send a force within 120 days to replace a small, ill-funded African Union (AU) force.

The council said it "takes note of" the request, and was willing to consider "at an appropriate time" a U.N. operation "subject to progress in the political process and improvement in the security situation on the ground."

The government of the Horn of Africa nation and part of the Eritrea-based Alliance for the Re-Liberation of Somalia signed a peace deal on Aug. 18, but it has been rejected by opposition hard-liners and done little to quell violence.

More than 8,000 civilians have been killed and 1 million uprooted in fighting since early last year which pits President Abdullahi Yusuf's government and allied Ethiopian forces against Islamist rebels. Anarchy has reigned in Somalia since a dictator was overthrown in 1991.

The existing U.N.-backed AU force in Somalia is meant to consist of 8,000 troops but has only 2,600 soldiers from Uganda and Burundi on the ground. Nigeria has promised another 850.

The Security Council has repeatedly fended off AU requests to send U.N. peace-keepers, leery of putting troops into a country where 18 U.S. soldiers and hundreds of Somalia militiamen died in a battle in 1993.

The incident inspired a Hollywood movie, "Black Hawk Down," and marked the beginning of the end for a U.S.-U.N. peace-keeping force.

Ban has already done some contingency planning, but this time the Security Council asked for "a detailed and consolidated description of a feasible multinational force" that would lay out its mandate and geographical scope.

It requested that he "urgently" identify and approach states that might contribute funding, troops and equipment.

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