Behind handshakes and smiles, Nato leaders are divided as they gather in Bucharest and the outgoing US president pushes for eastward expansion.

One of the biggest gatherings of world leaders, the 20th annual Nato summit is due to begin on Thursdsay in the Romanian capital.

George Bush is trying to persuade for membership of Nato to be extended to the former Soviet states, Georgia and Ukraine.

But with key allies like France and Germany opposing the plan for fear of provoking Moscow, Bush's final Nato summit could require some of his heaviest diplomacy.

Conflict of interests

The conflict of interests involves a delicate diplomatic dance between Nato's historic open-door policy and Russia's feeling that the alliances' borders are growing too close for comfort.

Nato was set up in 1949. It was an alliance to counter the military power of the Soviet Union.

Five years later the Soviets were refused membership.

The acceptance of West Germany led to the Warsaw Pact and a clear drawing of sides in the Cold War.

The pact dissolved in 1991 which began Nato's ongoing eastward expansion.

Shadow of Russia

At the Bucharest summit, Albania and Croatia too will begin the formal process of their membership.

But Russia casts a shadow over Nato's expansion plans.

Nato's backing of a US missile defence system in Poland and the Czech Republic has been harshly condemned by Vladimir Putin.

The Russian president will be making his first appearance at this year's summit to express his fears of a new arms race.

Jaap de Hoop Scheffer, Nato's secretary-general, says: "If President Putin comes to Bucharest with an open mind, it should be possible for us to advance a broader Nato-Russia relationship."

Nato says its eastward expansion will not threaten Russia.

Still, Jonah Hull, Al Jazeera's correspondent in Kiev, says Ukraine and Georgia are unlikely to be given this membership action plan in Bucharest.

"The problem they face even with President Bush's support is opposition both from Russia and from significant members of the Nato alliance.

"Russia has long been wary of Nato's expansion eastwards. It views it as a provocation and even says it will aim missiles at Ukraine if it goes ahead."

Other differences

Russia's differences with Nato go beyond the proposed eastward expansion.

Moscow is also upset by Kfor - a Nato-led peacekeeping force that remains in recently declared independent Kosova.

All of this has threatened to shift the focus of the Bucharest summit away from Afghanistan, supposed to be at the top of the agenda.

Nato leads more than 47,000 military personnel in that country.

Bush wants member countries to send more troops to Afghanistan.

Only a few countries have so far answered the call for more support to fight the Taliban in the south.

"The alliance must maintain its resolve and finish the fight ... we cannot afford to lose Afghanistan," Bush said in Bucharest during a speech at a German Marshall Fund conference on Wednesday.

He said that if the alliance does not stay on the offensive in Afghanistan, Taliban and al-Qaeda fighters will use it to launch more attacks on the West like those on September 11, 2001.

PHOTO CAPTION

U.S. President George W. Bush delivers a speech at the National Bank of Savings in Bucharest April 2, 2008.  

Al-Jazeera