"I am pleased that the United Kingdom is willing to step forward and volunteer for a leadership role," Powell told reporters.
CBS News Correspondent Elaine Cobbe reports Powell had been meeting with French leaders as his support-gathering tour draws to a close.
"France has shown a willingness to participate in that activity," he added. Vedrine said a French decision on its exact participation would be made "very soon."
Chirac's spokeswoman told reporters the decision would be made "with particular attention being given to the mandate, missions and organization of this force."
Powell arrived in London from Paris on Tuesday for talks on the peacekeeping issue with British Prime Minister Tony Blair. He is also expected to attend a ceremony marking three months since the September 11 suicide attacks on the United States.
The British government has so far declined to comment on speculation it would send 1,000-3,000 troops to Afghanistan to take part in a security force that could count 5,000 soldiers.
The peacekeeping force is expected to provide security in and around Kabul to protect the interim administration agreed at U.N.-brokered talks in Bonn last week and due to take office on December 22.
CBS News Correspondent Sam Litzinger reports the British government says it wants to make sure they have a clear mission and don't get caught up in a civil war. The deployment could begin in a few days.
Several international relief organizations also hope the force will help guard convoys and depots from bandits.
Powell said the make-up of the force, whose formation was delayed in part by U.S. misgivings over peacekeepers entering Afghanistan while its military operation there continues, had yet to be determined.
"It's important to get a U.N. resolution in place as quickly as possible. Then the roles of individual countries, those who will be leaders and those who will be willing to contribute forces to the international security force, can be worked out."
The 15-member U.N. Security Council plans to authorize the operation in a resolution being drawn up by U.S., French and British diplomats. They hope for adoption by Friday.
"It's important to get a U.N. resolution in place as quickly as possible, and then the roles of individual countries, those who would be leaders, those who will be willing to contribute forces to the international security force can be worked out," Powell said.
Germany has also offered to provide troops for the force and other countries expected to take part include Turkey, Italy and Canada. Jordan, which has worked with French troops in Bosnia, is seen as likely to join and Bangladesh is also ready to help.
France has offered its Charles de Gaulle aircraft carrier, combat ets, intelligence and logistical help to the U.S. Afghan campaign, although some domestic observers have scoffed at the limited scope of its overall contribution.
Powell said France was keen to play "a very active role" in subsequent reconstruction efforts for Afghanistan.
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