According to two of the sources, Slovakia, one of three NATO allies that have the S-300 missile defense system, wants assurances that the systems will be replaced immediately.
Any country providing S-300s is likely to receive the US-made Patriot air defense missile system to backfill the capability it would be giving up, according to two other sources familiar with the negotiations. Germany and the Netherlands have already publicly announced that they are sending Patriots to Slovakia. But integrating a new, complex air defense system into a country’s existing military architecture, as well as training its forces to use it, can take time, one source familiar with the matter cautioned.
Texas Rep. Michael McCaul, the top Republican on the House Foreign Affairs Committee, hinted publicly Wednesday that the US had made progress in getting Ukraine access to additional S-300s, an anti-aircraft weapon system that congressional sources say Ukraine is already operating effectively against Russia’s assault.
“I’ve been pushing hard for this,” McCaul told CNN’s Jim Sciutto. “I’m proud to say they do have S-300s going in now.”
An aide to McCaul later said he was referring to S-300 systems that have been owned and operated by Ukraine for years. Those systems are already in the country.
A senior defense official declined to comment on specific weapons systems or countries that might provide them, but noted that Austin was traveling to Slovakia to meet with the defense minister. The official said security assistance would be certainly a topic of discussion.
The Slovakian Embassy in Washington declined to comment. CNN has reached out to the National Security Council and the Defense Department for comment.
CNN reported earlier Wednesday that other Soviet-era air defense systems, including the SA8, have already been sent into Ukraine.
“People talk about a no-fly zone, they can create their own if we give them the military equipment and weapons,” McCaul noted.
Defense Secretary Lloyd Austin is scheduled to travel to Slovakia later this week after participating in the NATO Defense Ministerial in Brussels.
“At the request of President Zelensky, we have identified and are helping Ukraine acquire additional longer-range anti-aircraft systems and the munitions for those systems,” President Joe Biden said Wednesday as part of remarks detailing new security assistance.
Some US allies have also been leery of making their contributions to Ukraine public, multiple sources told CNN. Bulgaria and Greece also have more of the modern S-300 systems in question. Greece’s system is a different model than those currently operated by Ukraine, raising questions of whether additional training would be needed for it to be useful.
CNN’s Jim Sciutto contributed to this report.
