NATO tried to patch over divisions about the war in Afghanistan on Thursday but differences remained over the willingness of some members to contribute troops to the fight.

At a meeting in the Lithuanian capital Vilnius, defence ministers with troops fighting fierce battles against the Taliban in the south of Afghanistan backed calls by the United States for more countries to send forces there.

France said it was studying possible reinforcements and diplomats said Romania, Poland and Norway were among those who signalled they could do more. But, as widely expected, there was no formal offer of troops at the talks.

On a visit to frontline troops in the birthplace of the Taliban, U.S. Secretary of State Condoleezza Rice and British Foreign Secretary David Miliband also kept up the pressure on reluctant allies to share the combat burden.

Violence has risen sharply in the past two years in Afghanistan. Analysts say the country, which under the Taliban's hardline Islamist rule harboured al Qaeda before the Sept. 11 attacks, risks becoming a "failed state" again.

NATO Secretary-General Jaap de Hoop Scheffer said the 43,000-strong ISAF peace force in Afghanistan had made progress but acknowledged more needed to be done.

"I am cautiously optimistic," he said. "There are challenges, we need more forces ... the situation in Afghanistan means sharing responsibility and sharing risk."

U.S. Defence Secretary Robert Gates toned down his rhetoric, a day after saying NATO was at risk of splitting into members who are willing to "fight and die to protect people's security and those who were not".

But he stuck to his basic point that there was a contrast between nations such as the United States, Britain, Canada, the Netherlands and Denmark, doing most of the fighting in the south, and other NATO nations in safer parts of Afghanistan.

"I came away from the meeting encouraged," he said. "I think everybody understands the nature of the problem."

CANADA DEMANDS SOLIDARITY

Canadian Defence Minister Peter Mackay reaffirmed Ottawa's demand for an extra 1,000 troops ahead of a parliamentary vote next month that will decide whether it can prolong the mandate of its 2,500 troops in southern Afghanistan.

"We want to see more of a one-for-all approach," he said, adding Canada's demand for reinforcements was "non-negotiable".

French Defence Minister Herve Morin signalled a willingness to help Canada and a government spokesman said France was considering reinforcements. But Morin played down media reports that some 700 paratroopers could be deployed to the south.

"It's premature to announce such figures," he said, adding any final French decision could have to wait until a NATO summit in Bucharest April 2-4 - in other words, possibly not in time to influence the key Canadian vote on prolonging its mission.

In Afghanistan, Rice dismissed independent reports that Afghanistan risked becoming a failed state and said "remarkable progress" had been made. But she said the war would go on.

"This is a long war because the terrorists will not easily be defeated," she said.

On Wednesday, Germany said it would send around 200 combat soldiers to northern Afghanistan as part of a NATO Quick Reaction Force but would not move any of its 3,500 troops in the country to the south.

In Berlin, Chancellor Angela Merkel cautioned against differentiating between the contribution of individual NATO nations on the ground and insisted Germany was doing its bit.

"I think Germany has taken on a great deal of responsibility in Afghanistan," she told a news conference.

Rice and Miliband travelled to a military base in the southern city of Kandahar, the main city in Afghanistan's most volatile region. They met NATO commanders and troops before travelling to Kabul to meet Afghan President Hamid Karzai.

Both called for the speedy appointment of a senior figure as UN envoy to coordinate international efforts on Afghanistan after Karzai rejected Lord Ashdown for the role.