MOSCOW — Russia’s lower house of parliament has ratified a treaty with Syria that allows the Russian military to stay indefinitely in the Mideast country.

The Kremlin-controlled State Duma voted unanimously Friday to ratify the deal, which formalizes Russia’s military presence at the Hemeimeem air base in Syria’s coastal province of Latakia.

The move comes as a show of support for embattled Syrian President Bashar Assad. The deal allows Russia to use the base free of charge, and for as long as it requires.

Russia launched an air campaign in Syria a year ago, reversing the tide of war and helping Assad’s forces win back key ground. Moscow says its goal is to help the Syrian army fight terrorism.

Russia also has a naval base in Syria’s port of Tartus.