LONDON — Defense Secretary Robert Gates said today at the conclusion of a NATO meeting he notified the allies that they will be expected to share the cost of a planned expansion of the Afghan national army.

“I let a number of my colleagues know that we would be in touch in terms of the importance of sharing the cost of the increased size of the Afghan army because, after all, the effectiveness of the Afghan security forces — and in particular the army — in the long term is NATO’s exit strategy,” he said.

The Afghan army is to grow from the current 80,000 soldiers to 134,000 as part of a strategy for building a security force that eventually can stand on its own to prevent the country from again becoming a haven for terrorists.

Gates spoke with reporters after signing two agreements with his Czech counterpart. One laid out the legal basis for U.S. troops to operate a missile tracking radar in the Czech Republic; the other was on strategic defense cooperation. Both deals are linked to U.S. plans for developing a European-based expansion of a missile defense network. The radar would be linked to 10 missile interceptors based in Poland.

Improving Afghan governance and civic development are important elements of the U.S. and NATO strategy, Gates said.

“But turning security responsibilities over to the Afghans themselves at some future date is really the goal that we all have in mind and we need to be prepared to share the cost” of getting to that point, he said.

Earlier today, Gates participated in a NATO defense ministers meeting that focused on pushing forward with long-stalled plans to improve the alliance’s ability to better use military forces. The talks produced no new agreements but were intended to pave the way for decisions next spring.

The defense chiefs also discussed the implications of Russia’s armed incursion into Georgia in August.

British Defense Secretary Des Browne said NATO has shown a “unity of purpose” in response to the Russian incursion, but the alliance has fallen into “bad habits” in trying to adapt its military forces to 21st century warfare.

“We are lacking sufficient capabilities in key areas” such as airlift that would make the forces of each NATO member more useful beyond its own borders, Browne said.