Two former Soviet republics, Ukraine and Georgia, are hoping that during the summit they will be given the go ahead to enter the Membership Action Plan (MAP), a precursor for membership in the Western military alliance.
Russia, which is not a NATO member and has no right of veto in the organization, vehemently opposes the Western military alliance's expansion around its borders as it sees it as a threat to its national security.
U.S. President George Bush, who was on an official visit to Ukraine's capital, Kiev on Tuesday, has already signaled his support for Ukraine and Georgia's applications to enter the MAP.
However, according to sources in Brussels, some NATO members, including Germany, France, Spain, Italy, Portugal, the Netherlands, Belgium and Luxembourg oppose membership for Ukraine and Georgia as they are reluctant to antagonize relations with Russia.
France's Prime Minister Francois Fillon said in a radio interview Tuesday: "We think that it is not a good answer to the balance of power within Europe and between Europe and Russia."
The Kremlin threatened in February to target missiles at Ukraine if Kiev joins NATO and allows Western military facilities on its territory.
The summit participants are set to discuss U.S. plans to deploy an anti-missile system in Poland and the Czech Republic, which Moscow also considers a national security threat, Washington says the missiles will only be used in defense against 'rogue states' such as Iran.
The summit is also expected to focus on NATO's 47,000-strong peacekeeping operation in Afghanistan as the U.S. is urging NATO allies to send more troops to the conflict-stricken area.
NATO leaders are expected to invite Albania and Croatia to join the alliance, which is seen as a move to ensure stability in the region following Kosovo's declaration of independence.
Macedonia was also due to join its Balkan neighbors, but Greece has said it will veto Skopje's membership unless Macedonia changes its name.
The dispute over Macedonia's name has been going on for 17 years. Greece says that using the name, Republic of Macedonia, implies Skopje has territorial claims on Greece's northern province of Macedonia.
This meeting is expected to be the largest in the history of the Western military alliance as the Romanian capital is anticipating the arrival of about 60 heads of states and governments from NATO member nations and partners.
