Britain is prepared to take the risk of sending a “sizeable amount” of troops, to Mali and neighbouring West African countries as David Cameron offers strong support to France in its operation to drive Islamist militants from its former colony.

As news emerged that insurgents retreating from Timbuktu had set fire to a library containing thousands of priceless historic manuscripts, Downing Street said the prime minister told François Hollande on Sunday night Britain was “keen” to provide further military assistance to France.

Cameron despatched Sir Kim Darroch, his national security adviser, to Paris on Monday to discuss what help Britain could provide. Government sources said decisions on troop deployments were expected to be made in the coming days as France confirms its exact requirements. One source said that Britain could easily dispatch 200 troops if France requested such a number.