Russia is moving to expand its military presence in eastern Libya, a plan that could lead to a naval base, giving it a significant foothold on Europe’s southern doorstep.

A defense accord is being hammered out between Russian President Vladimir Putin and Libya’s eastern military commander Khalifa Haftar following their meeting in Moscow in late September, according to people briefed on the matter, who asked not to be identified discussing sensitive issues.

The escalation of Russian activity in Libya represents a fresh challenge to the U.S. and its European allies, which are already locked in a standoff with the Kremlin over its invasion of Ukraine and the country’s potential role in any wider Middle East conflict stemming from the Israel-Hamas war. Russia has been heavily active in neighboring Syria throughout that country’s decade-long civil war.