29 January 2013 12:57 GMT bbc.co.uk
The UK is to deploy about 350 military personnel to Mali and West Africa to support French forces, No 10 has said.
This includes as many as 40 military advisers who will train soldiers in Mali and 200 British soldiers to be sent to neighbouring African countries, also to assist with training.
Downing Street dismissed suggestions the move constituted "mission creep".
An international donors' conference in Ethiopia aims to finance the budget for the campaign, set at $950m (£605m).
Downing Street has repeatedly insisted there is no question of British units getting involved in fighting - but Labour has called for further clarity on what part the UK might take in the French-led mission.
Defence Secretary Philip Hammond has been updating MPs on the latest deployments in Mali in the House of Commons.
'What we can'
The UK is already sending a C17 transport plane for three months and an RAF Sentinel surveillance aircraft.
Number 10 said it would also allow the US to operate air refuelling flights out of Britain.
And it offered a roll-on, roll-off Merchant Navy ferry to help transport equipment to the French force in Mali. It would dock at a port in a West African state to enable the kit to be moved across land to Mali.
The UK has also offered to set up a combined joint logistics HQ in Mali, however so far the French have declined this offer.
A Number 10 spokesman said the UK government was doing what it could to support the French military intervention, "contributing to both Malian training and training forces that are involved in providing a regionally-led approach".
French-led troops are consolidating their position in the historic Malian city of Timbuktu after seizing it from Islamist extremists.
In Brussels later, defence officials are set to discuss details of the planned European Union-led training mission to build up the Malian army.
The BBC's Norman Smith says the British team of 40 military advisers is expected to be sent to Mali "fairly urgently".
Number 10 is also considering who will provide "force protection" for the military advisers.
At present, it is envisaged the force protection will not be provided by British soldiers. It is possible existing French forces in Mali could be used.
Separately, deputy national security director Hugh Powell is to discuss the potential UK contribution at an international donors conference for Mali hosted by the African Union in the Ethiopian capital, Addis Ababa.
Prime Minister David Cameron has assured French President Francois Hollande that Britain is "keen" to help Paris with its military mission.
The RAF has already provided two C17 transport planes and a Sentinel surveillance aircraft to assist France's operation.
Meanwhile, the UK's national security adviser, Sir Kim Darroch, was in Paris on Monday to discuss what further help the UK could provide to France's operation to drive Islamist militants from its former colony.
Mr Cameron has said the UK is ready to offer logistical, intelligence and surveillance help to France.
The French and Malian military said troops encountered little resistance when they entered the historic city of Timbuktu. They seized Gao, northern Mali's biggest city, on Saturday.
Islamist militants took the north of the country last year, but have been losing ground since French forces launched an operation earlier this month.
Shadow defence secretary Jim Murphy said it was important the UK supported the mission in Mali, but it is "not for us to put combat troops on the ground".
"We have to be very clear about how long we intend to be there [and] what it is we're seeking to achieve, so that the public, who are wary and weary after Iraq and Afghanistan, don't say 'Oh not again'," he said.
Mr Murphy also said British forces must be properly protected.
Military analyst Col Mike Dewar said the initial UK support was short term but its latest offer of help constituted a "much more long term plan".
It could take "years" for the British troops to make a difference to the "ill-trained" Malian army, he said.
Prof Michael Clarke, a director of the Royal United Services Institute think-tank, said the British involvement was a "politically important" gesture to illustrate Anglo-French military co-operation.
He said he could not discern a clear strategy at the moment in Mali, but he added: "That is understandable. In Libya we went in for humanitarian reasons and then a strategy evolved. That is what the French did, they went in initially for humanitarian reasons.
"I suspect the strategy [in Mali] will be to guarantee the cities are safe so that Islamists are kicked out and then let time do its work."
The former head of the Army, General Sir Mike Jackson, backed the government's position but warned that nations involved may face a "protracted guerrilla warfare".
"It doesn't really surprise me that the British government feels it needs to be seen to be helping," he told the BBC Radio 4 Today programme.
"We cannot let states fail because we know from recent history that failed states just lead to really difficult circumstances, instability."