Albania and Croatia are set to receive formal invitations to join. Macedonia is hoping to follow suit. And Ukraine and Georgia, both former Soviet republics that now have Western-leaning governments, are looking to receive Membership Action Plans (MAP), the first step toward becoming full-fledged NATO members.
Outgoing President Vladimir Putin will be present at the Bucharest events, even as NATO-Russian relations are under heavy strain.
For Russia, NATO expansion is a worrying development -- particularly when it involves members of its own post-Soviet neighborhood. Moscow views the MAP ambitions of Kyiv and Tbilisi with deep suspicion, as Vladimir Litovkin, an independent military analyst, tells RFE/RL's Russian Service.
"NATO-Russia relations today are at a low point in many respects. And I think it is not only the fault of Russia, but also the fault of NATO," he says. "It doesn't always hold an independent NATO position; it mainly follows the course set by the United States, which sees Russia, if not as an adversary, then certainly as a rival gaining strength."
Line In The Sand
Heading into Bucharest, the NATO allies appear divided on Ukraine and Georgia, with Germany and France opposing granting MAPs, in counterbalance to the United States.
Few expect the divide to be resolved by the close of the Bucharest summit. But Russia, which has already twice endured the ignominy of its former republics and Warsaw Pact allies entering the Western military alliance in 1999 and 2004, isn't taking any chances. The Kremlin has been waging a nonstop press campaign to remind NATO and the world that a friendly gesture toward Kyiv and Tbilisi may cost them dearly in Moscow's goodwill.
Dmitry Peskov, a spokesman for the Kremlin, told Reuters that Ukraine and Georgia's acceptance into NATO, if approved, would be a direct snub to Russia. "The realization of an 'open-door' policy toward Ukraine and Georgia will be a sign for us that the West has made its choice in favor of unilateral actions rather than forming trans-European institutions," he said.
Dmitry Medvedev, who becomes Russia's next president in May, said in an interview published last week that the situation surrounding Georgia and Ukraine is "extremely troublesome for the existing structure of European security."
Foremost among Russia’s concerns are U.S. plans to build parts of a missile-defense system in Poland and the Czech Republic, both NATO members.
The United States maintains the shield is necessary to monitor missile movements in unfriendly states, such as Iran and North Korea. The Kremlin, however, sees the shield as a threat to its own security, and fears the system may be expanded to include elements in Ukraine and Georgia, potentially taking U.S. military equipment within kilometers of its own border.
A Problem Of Mind-Set
Aleksandr Golts, a military expert and editor of the "Yezhednevny zhurnal" online newspaper, says the real reason Russia is opposed to NATO expansion is more basic.
"I don't think, in fact, that this is a military problem, although Russia constantly talks of the military threat, of the construction of some sort of mythical NATO bases in Georgia and Ukraine," he says. "The problem here is one of foreign policy or, if you like, one of psychology."
In 2000, as Putin assumed the Russian presidency, one of Russia's foreign policies was to improve ties with its close neighbors. But the reality, Golts says, turned out somewhat differently, with colored revolutions in Georgia and Ukraine that saw pro-Western reformers ousting their Russia-friendly leaders.
"Ukraine and Georgia's desire to join NATO flies in the face of this policy," Golts says. "They have no desire to compete for the role of younger brother in exchange for cheap energy supplies. This is a sign of defeat for Russia's foreign policy, and that's what irritates the Kremlin more than anything."
All eyes will be on Putin, who is set to address the NATO summit at its close on April 4. Will he strike a conciliatory note as an outgoing leader, or repeat the fierce rhetoric of his 2007 Munich speech, in which he accused the United States of trying to impose its will on the rest of the world?
NATO Secretary-General Jaap de Hoop Scheffer has expressed hope that Putin will abstain from "unhelpful rhetoric" during his time in Bucharest. Many commentators believe the outgoing leader will in fact want to maintain a cordial tone as his two terms as president come to a close. Even after Putin's departure, however, Russia's opposition to a broader NATO is likely to remain unyielding.