Russian President Vladimir Putin has for many years pushed for closer ties with Belarus under the auspices of a unified state, and raised the idea again last month.
Lukashenko has in the past rejected such moves, accusing Russia of wanting to swallow up his country, but now faces protests and the threat of Western sanctions over an Aug. 9 presidential election which opponents say was rigged.
Russia has stood by Lukashenko throughout the protests and says he will visit Moscow for talks in the coming days.
“(Russia) will now quickly finish what they weren’t able to for 20 years, and it is very worrisome”, Lithuanian Foreign Minister Linas Linkevicius said in televised comments.
The process of integration between the two former Soviet republics “can hardly be stopped”, he said, adding that Lukashenko, who denies electoral fraud, had “neither moral nor political justification to do that”.
Linkevicius, whose country declared independence from the Soviet Union in 1990 and is now a member of the European Union and NATO, said a closer relationship between Minsk and Moscow could lead to Russian military being based in Belarus.
Such moves would require a “mandate from the people”, without which it would be “a route towards more tensions,” he said.
(Reporting By Andrius Sytas, Editing by Timothy Heritage)