WASHINGTON — The United States has asked Vietnam to stop allowing Russia to use a former US base to refuel nuclear-capable bombers engaged in shows of strength over the Asia-Pacific region, exposing strains in Washington’s steadily warming relations with Hanoi.

The request, described to Reuters by a State Department official, comes as American officials say Russian bombers have stepped up flights in a region rife with tensions among China, US ally Japan and South-east Asian nations.

General Vincent Brooks, commander of the US Army in the Pacific, told Reuters the planes had conducted “provocative” flights, including around the US Pacific Ocean territory of Guam, home to an American air base.

…Dr Bernard Loo from the Military Studies Programme at S. Rajaratnam School of International Studies (RSIS) posited that Hanoi’s decision to grant Moscow access to the base had been driven by its desire to offset Beijing’s power in the South China Sea, but added that it is “a strange policy on Vietnam’s part, especially given the warming Sino-Russian relationship”.

…Dr Evan Resnick, assistant professor and coordinator of the U.S. Programme at RSIS, told TODAY in an interview that this is a signal to America and its allies to back off from interfering in Ukraine. “While Russia’s economy is in shambles and its conventional military is quite weak, it is still a nuclear power. These sorties by Russia’s nuclear bombers are clearly calculated to project its core strategic strength,” Dr Resnick said.