Thousands of troops, backed by hundreds of tanks, artillery and other heavy weaponry, began rumbling through the North Caucasus on Monday, as Russia began its largest military exercises since last year's war with Georgia.

The Caucasus 2009 war games are being seen by many experts as a warning shot for nearby Georgia, where the government says it has rearmed armed forces and where NATO recently wrapped up its own exercises.

Experts say the exercises may also be signal to the United States that Russia will give no ground on its efforts to maintain an exclusive sphere of influence in Georgia and other former Soviet republics. The games run through July 6 -- the day that President Barack Obama arrives in Moscow for a highly anticipated summit with Russia's Dmitry Medvedev.

Defense Ministry official say more than 8,500 troops will take part, along with nearly 200 tanks, armored vehicles, 100 artillery units and several units from Russia's Black Sea naval fleet.

The exercises, which are being personally overseen by Gen. Nikolai Makarov, the chief of Russia's General Staff, are structured around a theoretical crisis situation that spirals out of control into open fighting, the ministry said.

Tensions remain high between Russia and Georgia, which lost authority over the regions of South Ossetia and Abkhazia during the war in August. Russia has been building military bases, storage facilities for supplies and roads in the two regions, which Moscow recognized as independent, and around 6,000 troops are based in each region.

Moscow has been openly hostile to Georgia's ambitions to join NATO and has signaled that it would not tolerate any other ex-Soviet republics from joining the alliance.

Still, Georgian President Mikhail Saakashvili has not backed down on his drive for NATO membership and his efforts to draw closer to the United States.

Last month, NATO wrapped up a month of its own training exercises in Georgia, though just a few hundreds troops participated. Despite the small size of the games, Russia was irked, calling them a provocation.

Deputy Defense Minister Col. Gen. Alexander Kolmakov was quoted by Russian media on Monday as saying that the Caucasus 2009 exercises were adjusted as a result of the NATO games and would be "quite major, as compared with those that were conducted in Soviet times."

NATO and Russia over the weekend agreed to resume military ties that had been frozen after the Georgian war.