With strong U.S. backing, overwhelmingly Muslim Turkey officially agreed Monday to take command of the peacekeeping mission in Afghanistan. The change supports Washington's position that the war against terror is not between Islam and the West.

The Turkish government said it would take command of the 4,500-member, 18-nation force from Britain for six months, but gave no date. British officials said they did not believe that a handover would take place before June.

"The date of the takeover will be determined following negotiations with Afghanistan, Britain and the United Nations," Cabinet spokesman Yilmaz Karakoyunlu said.

The announcement came after Defense Secretary Donald H. Rumsfeld sent a letter to the Turkish government assuring full U.S. support if Turkey takes command of the force, private NTV television reported.

Turkey has some 270 peacekeepers in Afghanistan and is the only Muslim country that has contributed to the force, which is responsible for patrolling the capital, Kabul.

The United States had been strongly encouraging Turkey, NATO's sole Muslim member and a staunchly secular state, to head the force.

Washington sees Western-oriented Turkey as a role model for Afghanistan. Turkey's leadership of the force would also support Washington's argument that the fight in Afghanistan is a battle against terror and not a clash between Islam and the West.

In London, British Defense Secretary Geoff Hoon welcomed the Turkish announcement and said a British contingent would remain with the force after Turkey took over leadership.

Britain has led the force since the Security Council established it in late December and had wanted to hand over command in April.

For months, Turkey has considered taking command of the force, but was concerned that the mission would be too costly for a nation experiencing a sharp economic crisis.

Turkey was also concerned over Afghan demands that the force should be expanded throughout the country to stop regional warlords from vying for power.

Turkey's financial concerns seem to have been met in March, when U.S. Vice President Dick Cheney visited and promised that the Bush administration would ask Congress for $200 million in economic aid and $28 million in military aid for Turkey.

The Turkish announcement said that the force would continue to be responsible only for security in Kabul.

Turkey has said that it would enlarge its force to about 1,000 troops if it assumes command.

Turkey has a strong history of participating in peacekeeping missions.

A Turkish general headed the mission in Somalia, although Turkey did not have a significant number of ground troops as part of that mission.

Turkey also sent peacekeepers to mostly Muslim Kosovo and Bosnia.

Turkey regards Central Asia as part of its sphere of influence and has had ties with Afghanistan for decades.

In the 1920s, Turkish military officers were sent to Afghanistan to train the military there. Turkey has been sending medical aid to Afghanistan for years and a Turkish-supplied hospital in Kabul has stayed open throughout the rise and fall of the Islamic Taliban militia.