MOSCOW - Russian Foreign Minister Sergey Lavrov says the airstrike that the United States launched at a Syrian military base earlier this month damages the prospects of a political settlement for the war-torn country.

The airstrike was in response to a chemical weapons attack on April 4 on a northern Syrian town that Washington blamed on the Syrian government.

Lavrov told a security conference on Wednesday the attack as a pretext for a regime change in Syria and said the U.S. response "pushes the prospect for a wide international front on terror even further away."

Defence Minister Sergei Shoigu said earlier on Wednesday Russia had to boost security measures at its air base in Syria after the airstrike. Russia has provided an air cover for the government's offensive on Islamic State militants.