"We've been in discussion with the United States, with Ukraine and also with other allies on the possibility to deploy or to send altogether our S-300 systems to the Ukrainians," Slovak Defence Minister Jaroslav Nad told reporters.

"We're willing to do so immediately when we have a proper replacement," he added alongside US Defence Secretary Lloyd Austin in Bratislava.

Nad said that handing over "the only strategic air defence system that we have in Slovakia" would "create a security gap in NATO".

"But yes, should there be a situation that we have a proper replacement or that we have a capability guaranteed for a certain period of time, then we would be willing to discuss the future of the S-300 systems," he added.

Austin confirmed there were talks on the matter but said he had no announcements to make.

"These are things that we will continue to work with all of our allies on and certainly this is not just a US issue. It's a NATO issue," he told reporters.

Earlier Thursday, Nad mentioned that Slovakia was still dependent on Russia for the servicing of the S-300 system.

"I wonder how we should service it, modernise it, provide spare parts when a country that can do so is a war aggressor and any cooperation with that country is impossible?" Nad told reporters alongside his Slovenian counterpart.

"Slovakia needs to get rid of this dependence on Russia as soon as possible," he added.