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In more than two decades in power, the autocratic leader of Belarus has cast his nation as Moscow's closest ally, securing tens of billions of dollars in Russian subsidies.

At the same time, President Alexander Lukashenko has skillfully exploited Russia's security fears by occasionally reaching out to the West to win concessions from Moscow. Now, the Kremlin finally seems to have lost patience with its unruly ally, spelling an end to a relationship that has been described as giving away "oil for kisses."

The spiraling conflict between the neighbors has reached such a level that some analysts have talked about Russia possibly staging a "palace coup" against Lukashenko. Visibly nervous about Russia's intentions, the Belarusian leader recently assured his nation of 10 million people that "there will be no war" between the two countries.

Lukashenko has sought to present Belarus as an indispensable partner for Russia and a bulwark against NATO. At the same time, he has periodically made overtures to the West, masterfully exploiting Moscow's fear of losing a crucial ally to win more financial aid.

It now seems that Russian President Vladimir Putin has grown tired of Lukashenko's games. A scheduled meeting between the two last week was postponed indefinitely, and Russia has set up border controls on its previously unguarded frontier with Belarus.

Putin and Lukashenko never got along, and it's hard to imagine any affinity between the cold, reserved former KGB officer and the blustery and boisterous Belarusian, a former state farm director.

Lukashenko has led Belarus since 1994, extending his rule through elections the West has criticized as undemocratic, keeping most of the economy in state hands and relentlessly cracking down on the opposition and independent media.

But Belarus' dependence on Russia and Moscow's desire to keep a key military ally on its western flank have helped bridge differences — until recently.

When Belarus balked last year at the price Russia charged for its natural gas, accumulating a $550 million debt, Moscow hit Minsk in its softest spot by sharply cutting oil supplies. Since the 1991 collapse of the Soviet Union, Belarus had used cheap Russian crude for products that accounted for more than a third of its export revenues.

The spat escalated with Lukashenko recalling Belarusian representatives from a Russia-dominated economic alliance and ignoring its recent summit. He then raised the stakes by abolishing visas for short-time travelers from 80 nations, including the U.S. and the European Union. The move vexed Russia, which voiced concern that foreign visitors could cross the uncontrolled border with Belarus.

Moscow responded by unilaterally establishing border controls — a move Lukashenko warned could trigger a "serious conflict."

He further challenged the Kremlin by ordering his interior minister to open a criminal inquiry against Russia's top sanitary official for barring imports of Belarusian food products. Russia has banned some agricultural imports from Belarus, accusing it of becoming a conduit for contraband Western food banned in retaliation for the U.S. and the EU sanctions against Moscow.

The Kremlin responded that the Russian official was only doing his job, and noted that deliveries of cheap oil to Belarus had cost Russia over $22 billion in lost revenue in 2011-15. The cheap energy, along with billions of dollars in Russian loans, buttressed Belarus' Soviet-style economy that has relied on its eastern neighbor as its main export market.

Russia and Belarus have had economic disputes before, but each time Moscow caved in to Lukashenko's demands and restored the subsidies. The latest controversy, however, seems deeper, and Putin appears unlikely to back off.

"There are limits to a weak state's ability to dictate its terms to a stronger one," economic expert Vladislav Inozemtsev said on Moscow's Ekho Moskvy radio.

Lukashenko sounded unusually tense at a recent news conference.

"Why take us by the throat?" he asked.

"No one will occupy us, no one will send in troops," he said in an apparent reference to fears that Russia could try to use massive joint military maneuvers scheduled in Belarus later this year to overrun the country. "The Russian troops that will enter Belarus will leave."

The statement seemed to reflect Lukashenko's suspicions about the Kremlin's intentions following Russia's annexation of Ukraine's Crimean Peninsula in 2014 and support for pro-Russia separatists in eastern Ukraine.

Lukashenko never recognized Crimea as part of Russia, and he also refused to follow suit when Moscow acknowledged Georgia's breakaway provinces of South Ossetia and Abkhazia as independent states after a brief war between Russia and Georgia in 2008.

The Center for Strategic and Foreign Policy Studies in Minsk warned recently that the Kremlin could try to send troops into Belarus.

"The threat of Russia stirring up an internal conflict in Belarus has reached a maximum level," said Yuri Tsarik, the head of the center's Russia program.

For several years, Lukashenko has firmly resisted the Kremlin's push for Belarus to host a Russian air base, probably fearing it might serve as a foothold for Moscow as in Crimea, where Russia had leased a navy base prior to the annexation.

"Lukashenko remembers quite well that the seizure of Crimea began from the Russian base," said Minsk-based analyst Valery Karbalevich. "After Crimea, Minsk has sensed real danger, and Lukashenko has started searching for ways to resist the Russian pressure."

In a bid to counter Russia, Lukashenko has sought to mend ties with the West, and he scaled back his crackdown on dissent.

The EU and the U.S. recently rolled back sanctions they imposed on Belarus following relatively smoother elections and the release of political prisoners. But Belarus' hope of securing a $3 billion IMF loan has remained elusive.

"Lukashenko needs Moscow, and the Kremlin knows that," said Alexander Klaskovsky, an independent political scholar in Minsk. "In exchange for subsidies, Putin expects Belarus to show support and discipline, not wag its tail to the West."

He predicted Putin would be unlikely to resort to force.

"The Kremlin's strategy is to scare Lukashenko and then make a deal with him, putting him on a shorter leash," Klaskovsky said.

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Isachenkov reported from Moscow.