MINSK, Belarus — Western officials and the news media have for years routinely described President Aleksandr G. Lukashenko of Belarus as “the last dictator of Europe.”

So it may have been jarring for some to hear him expressing deep support for human rights, democracy and the rule of law in an address last month to a large group of United States and European lawmakers who came for a conference to Minsk, the country’s tidy, but utterly uniform, capital.

For Mr. Lukashenko, however, the performance was old hat.

Over two decades, he has perfected the art of playing Russia and the West against each other. Belarus has been both an indispensable ally and ward of the Kremlin, depending on Russian subsidies to keep its economy afloat, and an important buffer for the West against the Kremlin’s growing military aggressiveness.

But with major Russian military exercises scheduled for next month in Belarus, opposition leaders, analysts and even the American military fear that Mr. Lukashenko’s tightrope act may be coming to a close.