He told MPs all conditions had now been met to send the extra personnel and that eight other countries had also offered additional troops.

The UK force level will reach 9,500 but special forces takes this to 10,000.

Mr Brown and Barack Obama are holding a video conference to discuss the issue a day before the US president's likely announcement of 35,000 extra US troops.

'Political surge'

Meanwhile a soldier from 1st Battalion, Coldstream Guards has died after being injured in an explosion in Helmand province - the 236th British fatality in Afghanistan since operations began in 2001, and the 99th this year.

Defence Secretary Bob Ainsworth has confirmed at least 5,000 additional Nato troops will be sent to the country.

He told the BBC the eight countries to pledge extra forces include Turkey, Solvakia, Georgia and Portugal, but he believed others would follow.

A Nato spokesman said there would be more announcements at a meeting in Brussels on Thursday and Friday.

Mr Brown told the Commons the three conditions needed to commit UK troops had been met, namely enough equipment, sufficient help from other nations and more local training for local forces.

A political surge would follow the military surge, he added, with an enlarged and reformed Afghan police force and more effective and accountable local administration.

He said the coalition was seeking a "major" expansion of the Afghan army from 90,000 to 134,000, with the aim that local forces would eventually assume sole responsibility.

He also said the terrorist threat from al-Qaeda would be addressed at its source - along the Afghan/Pakistan border areas.

'Britain's safety'

He said: "We should be failing in our duty if we didn't work with our allies to deal with the problem where it starts.

"The safety of people on the streets of Britain requires us to deny al-Qaeda the space to operate across Pakistan and deny them the option of returning to operate in Afghanistan."

Mr Brown said the troops would be deployed in "early December" and Britain's "highly professional" special forces would play their "full role" in taking the fight to the Taliban.

The prime minister also said the first districts could "potentially" be handed over to Afghan control next year depending on training and policing.

But Conservative leader David Cameron warned against setting a timetable for a handover to Afghan forces and the withdrawal of British troops.

He said: "We must never do or say anything that gives the impression to the Taliban that we will not see this through.

"Nor should we raise any false hope, or any false expectation amongst the families of British forces, that may later be dashed."

Among the regiments to deploy extra troops "shortly" is 1 Royal Welsh, which will form part of 11 Light Brigade.

Lt Col Nick Lock, 1 Royal Welsh commanding officer, said: "We are well trained and my soldiers will be meeting the challenges head-on with the appropriate kit and bags of determination.

"We are grateful for the support from not only our families, but the general public - a huge source of morale for us all."

Newly arrived Merlin helicopters have been approved for operation a month ahead of schedule.

And Mr Brown said the number of mine-resistant Mastiff vehicles would have almost doubled by the end of the year, compared with August.

The amount spent from the Treasury reserve on equipment and support for each individual soldier would rise from £190,000, three years ago, to £400,000, he added.

BBC defence correspondent Caroline Wyatt said that after constant negative headlines about shortages of equipment and helicopters in Helmand, the government has been keen to show that the extra troops have what they need before they are deployed.

But she said the one thing that still worried military chiefs was the fall in public support for the mission which they believed may affect those on the

front lines

WT+BBC.