Russia has reiterated its threat to target arms shipments to Ukraine, with foreign minister Sergey Lavrov saying Friday that any cargo believed to be carrying weapons are “fair game” while vowing to block the transfer of Soviet-era S-300 air defense systems to Kyiv. “Any cargo moving into Ukrainian territory which we would believe is carrying weapons would be fair game,” Lavrov said in an interview with Russia Today. Slovakia has said that it is ready to send its S-300 system to Ukraine “immediately” provided that it receives a replacement to protect its own airspace. “We’re willing to do so immediately when we have a proper replacement,” said Jaroslav Nad, Slovakia’s minister of defense, at a joint press conference with U.S. Defense Secretary Lloyd Austin on March 17. The S-300 is Slovakia’s only strategic air defense system, he said, adding that handing it over to Ukraine would create a “security gap …