Moscow is recruiting Syrians skilled in urban combat to fight in Ukraine as Russia’s invasion is poised to expand deeper into cities, according to U.S. officials.

An American assessment indicates that Russia, which has been operating inside Syria since 2015, has in recent days been recruiting fighters from there, hoping their expertise in urban combat can help take Kyiv and deal a devastating blow to the Ukraine government, according to four American officials.

The move points to a potential escalation of fighting in Ukraine, experts said.