Ukraine says it is ready to share information from its missile warning system with Western countries.
Saturday's announcement comes as tensions mount between Russia and the West over the conflict in neighboring Georgia.
It also comes just days after Poland and the U.S. signed a deal to set up part of a missile defense system in Poland.
Ukraine's Foreign Ministry says the demise of a Russian-Ukrainian bilateral defense agreement allows it to make new deals with Western countries on missile warning systems and satellite tracking.
On Saturday, Ukrainian President Viktor Yushchenko called for talks with Russia on the Black Sea Fleet's use of a Ukrainian port.
Mr. Yushchenko expressed concern that Russia's use of the port Sevastopol could inadvertently drag Ukraine into Russia's conflict with Georgia.
The Ukrainian leader signed an order Wednesday requiring Russia to seek Ukraine's permission moving warships to and from the port. Moscow rejected the decree, describing it as "anti-Russian."
Russia has an agreement to use the Ukrainian port until 2017, but Ukrainian officials say they want the Russian fleet to leave when the lease expires.
Some information for this report was provided by AFP and Reuters.