Pierre Lellouche, a parliamentarian from Sarkozy's centre-right UMP party and an international affairs expert, will work with envoys from the United States, Britain and Germany, Sarkozy said.

"The Afghan crisis and Pakistan instability now form the same problem," Sarkozy wrote in an open letter to Lellouche, saying the situation posed a major threat to global security.

"Our priority is to prevent the re-establishment of a radical regime in Afghanistan, the destabilisation of Pakistan and to reduce the terrorist threat which is centred in this region," he added.

U.S. President Barack Obama has pledged to make Afghanistan a foreign policy priority for his new administration and has named Richard Holbrooke as his envoy to the region.

Britain and Germany swiftly followed suite, signalling their willingness to work closely on the issue with Obama.

Washington is working on a review of its Afghan policy that is expected to provide a new strategy plan ahead of a summit of NATO leaders in France in early April.

The United States has 38,000 troops in Afghanistan and announced plans last month to send another 17,000 that NATO commanders say are necessary to stabilise the country against an intensifying Taliban insurgency.

Other NATO countries have supplied just over 30,000 troops, with Britain, German and France the largest contributors after the United States. Washington wants its allies to send additional temporary forces.

France says force alone cannot resolve the problem and French Defence Minister Herve Morin said on Monday he wanted NATO to set a date for starting the withdrawal of its forces from Afghanistan, once a new strategy is agreed upon.