LONDON - Prime Minister Gordon Brown on Wednesday urged Taliban fighters to down their arms and join Afghanistan's political process, saying they had a legitimate role to play.

The announcement came as the Afghan flag was raised over the southern Afghanistan town of Musa Qala after a successful five-day battle by Afghan troops, backed by British and American forces, to drive the Taliban out of a former stronghold.

Brown, who held talks with President Hamid Karzai in Kabul this week, said negotiation with the Taliban was not an option, but realism was needed when tackling the insurgency that has rumbled on for nearly six years.

"If they are prepared to renounce violence and abide by the constitution and respect basic human rights, then there is a place for them in the legitimate society and economy of Afghanistan," Brown told parliament.

The prime minister's announcement came as he unveiled what he called a new framework on Afghanistan, with plans to provide assistance of about 450 million pounds between 2009 and 2012 and to bolster training of Afghanistan's armed forces.

Senior British government sources said the process would also involve Afghan leaders reaching out to lower-level Taliban who might be looking to escape the movement, but would not involve anyone negotiating with top-level insurgent leaders.

"This is about splitting the Taliban," one source said.

Brown said Karzai had told him that already 5,000 fighters had laid down their arms. The government sources said the ex-Taliban fighters were affiliates and associates of the movement, rather than hard-line members.

Other elements of the plan involve trying cut poppy production, used to make heroin, which generates vast amounts of money, much of which funds the insurgency. Afghanistan is the world's largest producer of poppies.

Other parts of the plan will involve encouraging the Afghan government to take more responsibility, and for other nations among the 38 operating in the country to bear a greater burden.

One of the largest tasks will involve training up the Afghan army. There are currently about 50,000 soldiers in the force, but it is incapable of operating without substantial backing and also needs more equipment, training and logistics.

Brown said the aim would be to train around 20,000 more troops in the next year, with British army mentors joining units in order to ensure their efficacy.

However, officials said that even with extensive training and investment, the Afghan national army was unlikely to be able to operate autonomously until at least 2012, and even then "there will probably be the need for some support".

Britain, which has about 7,800 troops operating in Afghanistan, part of a 40,000-strong NATO stabilisation force, is expected to increase that number over time as it draws down in Iraq, but no formal announcement has been made.