MOSCOW (AP) — President Dmitry Medvedev said Wednesday that Russia and its ex-Soviet allies wanted to cooperate with the United States on stabilizing Afghanistan but he appeared to link any help to changes in Western policy. Saying Moscow and its allies “are ready for full-fledged, comprehensive cooperation,” the Russian leader seemed to imply that Moscow’s help on Afghanistan was contingent on a broader list of changes it wants from the new U.S. administration. These include a halt to NATO enlargement in Europe and the cancellation of plans for a U.S. missile-defense system on Russia’s western borders.