SIAULIAI, Lithuania — As American antiaircraft batteries test alongside NATO allies in the Baltics, Russian troops conduct exercises in beleaguered Belarus, worrying some allies that Russian President Vladimir Putin is aiming for a permanent troop presence on NATO’s eastern flank.

“Let’s not have any illusions regarding Russia,” Lithuanian Defense Minister Raimundas Karoblis told the Washington Examiner at the Defense Ministry in Vilnius Thursday. “The present administration is going to regain influence over the countries in close proximity to them.”

Belarusian President Alexander Lukashenko has faced hundreds of thousands of protesters each week since fraudulent elections in August. As a last-ditch effort to hold power, the idea of a “unity state” that would join Russia and Belarus is again on the table.

“Lukashenko wants to stay in the position and, of course, asks, expects the support of the Russian side,” Karoblis explained.

Wojciech Lorenz, a security analyst at the Warsaw-based Polish Institute of International Affairs, said that Moscow is intent not to let Belarus slip from its sphere of influence.

“It is Russia's vital interest to maintain political control over Belarus,” he told the Washington Examiner. “It is worried by the developments but does not want to intervene as it could do more harm than good to her interest.”

Lorenz explained that Belarusians are not anti-Russian, as they share a common language and heritage with Russia.

“They also do not want to join NATO or EU,” Lorenz said. “They just do not want to be ruled by the dictator who prosecutes, tortures, and murders his opponents. So they want a change. But such a change does not necessarily have to infringe Russian interest.”

Lukashenko has proposed, and Moscow has embraced, the idea of changes to the Belarusian Constitution. Such changes could limit Lukashenko’s power and ensure Russia’s control over Belarus.

“The worst-case scenario would be the deployment of Russian troops to Belarus, which could further increase the Kremlin’s ability to intimidate NATO eastern members,” Lorenz said.

Marius Laurinavicius, a Russia security expert at the Vilnius Institute of Political Analysis, told the Washington Examiner that Russia would benefit from a corridor linking its exclave in Kaliningrad to the rest of Russia.

“Strategically, Russia is interested in having a corridor from Kaliningrad to Belarus,” he said.

Aside from economic and political benefits, Laurinavicius said that Russia is using the same argument it did when it annexed Crimea in 2014.

“If you remember this narrative in Ukraine, that they need a corridor from Mariupol to Crimea, it's the same station,” he said. “They really need this corridor to make Kaliningrad secure.”

Former Ambassador John Herbst of the Atlantic Council told the Washington Examiner that he believes Russia is still weighing the cost-benefit of deploying troops.

On the one hand, Moscow must prevent a popular democratic uprising in Belarus that could serve as a model for Russians to overthrow Putin.

“But in the long run, they may have a larger problem. They may turn the Belarusian people against them for generations,” he said.

“We can't rule out Russian troops going in,” he said. Such a move would create a trying scenario for the United States.

“We have a commitment to defend all of our NATO partners," he said. "So, we'd rather not see Russian troops, more than are already there, in Belarus."

Meanwhile, behind the white stone walls of the Defense Ministry in Vilnius, policymakers are bracing for the possibility that Lukashenko colludes with Moscow to secure his position in Minsk.

“The danger and the risk is that the price would be the deployment of Russian troops permanently in Belarusian territory,” Karoblis said. “Potentially, with the so-called creation of the union state between Russia and Belarus, I can’t say the annexation of Belarus by Russia, but nevertheless absorption.”

He added: "It’s definitely a threat for NATO, for the West."