His remarks came a day after the Russian newspaper Kommersant reported that Moscow could soon start to deliver S-300 systems to its ally Damascus, and cited a source as warning of "catastrophic" consequences if they were attacked.
"What's important to us is that the defensive weapons the Russians are giving Syria won't be used against us," Lieberman told the news website Ynet.
"If they're used against us, we'll act against them."
Russia and Syria signed an accord in 2010 for the S-300 system but the missiles have not been delivered because of Israeli pressure, according to Kommersant.
Russian Foreign Minister Sergei Lavrov said earlier this month that no decision had yet been taken on the S-300 missiles.
"We have an open line; we really do have discourse" with the Russians, said Lieberman, noting that their systems had never been used against Israel .
"For several years we've been constantly in coordination and able to avoid friction with the Russians." APP/AFP