NATO defense ministers have opened two days of informal talks expected to focus on the alliance's expanding mission in Afghanistan and modernization of its forces.

As he arrived in Berlin for the meeting, U.S. Defense Secretary Donald Rumsfeld called for more flexibility for NATO troops carrying out their Afghan mission.  He specifically suggested that the alliance, over time, develop an anti-terrorist capability.  He said the capabilities of individual NATO countries should be adapted on an alliance level.

U.S. officials say Mr. Rumsfeld will urge removal of individual national restrictions on what NATO troops can do and where they can go, especially in regard to the rules of engagement.

Among other topics, the Berlin meeting is expected to review NATO funding and the importance of maintaining what U.S. officials call a "productive relationship" with Ukraine.

Officials say Mr. Rumsfeld also will thank U.S. allies for their support following Hurricane Katrina.

Some information for this story provided by AP and Reuters.