Lukashenko said he had ordered half the army to enter combat preparedness and had agreed with Russian President Vladimir Putin that their troops could unite in the event of a threat from the West.
"If they (NATO troops) don't hold still, it's necessary to use a joint grouping of armed forces, the basis of which is the Belarusian army," Lukashenko said. "The Russians must support us and follow us."
Belarus is Russia's closest ex-Soviet ally, and its territory is an integral part of Moscow's European defense strategy.