BRUSSELS, March 6 (Reuters) - The United States increased pressure on NATO allies to support Canadian troops battling Taliban insurgents in south Afghanistan, and France said on Thursday it was still considering such a move.

In what would be a major blow to the 43,000-strong NATO-led force, Canada has said it will pull its 2,500 troops out of the southern province of Kandahar next year unless allies come forward with an extra 1,000 soldiers to support it.

"The Canadians have made it clear they desire a partner in the south and we believe that the alliance has an obligation to deliver on that because this is a NATO mission," U.S. Secretary of State Condoleezza Rice told a news conference after talks at NATO headquarters.

France, whose 1,900 troops are primarily in the capital Kabul, indicated last month it could be ready to help Canada although alliance sources said subsequently it could send hundreds of ground troops to east Afghanistan instead.

"The choice has not been made between the east and Kandahar," French Foreign Minister Bernard Kouchner told reporters.

"We are aware both of the needs of Kandahar in the south and of the east." The final decision will lie with President Nicolas Sarkozy and the army.

While the east is regarded as more dangerous than the relatively calm capital Kabul, the fiercest battles have been in the southern provinces of Kandahar, Uruzgan and Helmand.

Washington is heading a campaign for what it calls a fairer sharing of the burden in the fight against Taliban insurgents. Britain, Canada, Poland and others have backed the U.S. demand and want to see decisions by a NATO summit in April.

One option being discussed is for the deployment of French soldiers to the east to free up U.S. forces there to go and help Canadian troops in the south. The United States has not said publicly whether such a possibility is feasible.

Alliance sources say Poland is keen to take on more responsibility in the east, perhaps raising its presence by several hundred to 1,600, while Britain is understood to be considering raising its presence by up to 600. (Reporting by Mark John; Editing by Robert Woodward)

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