NATO defense ministers are to examine reforms of the alliance to help it meet modern threats. Secretary-General Jaap de Hoop Scheffer has been calling for a new "strategic concept" that would help NATO face the dangers of the 21st century. The ministers will also look at the membership aspirations of Georgia and Ukraine, which have added to tensions with Russia. The ministers gathered Friday for their second and final day of a meeting in Krakow, Poland. US Defense Secretary Robert Gates on Thursday played down Kyrgyzstan's decision to kick the US off a strategic air base it depends on to supply troops in Afghanistan. He said the US would be willing to pay higher rent but said the base was ultimately replaceable.