KANDAHAR AIRFIELD, Afghanistan  – Prime Minister Gordon Brown vowed a renewed effort to defeat the Taliban insurgency in Afghanistan as he made an unannounced visit to troops in the field Sunday.

Brown made the visit two weeks after ordering the deployment of 500 extra British troops to Afghanistan alongside a surge of 30,000 US forces, part of a sweeping new strategy to turn around the eight-year war.

He held talks with Afghan President Hamid Karzai at a military base in Kandahar, the southern province where the Taliban first emerged and one of the deadliest battlefields for Western troops since the 2001 US-led invasion.

Brown spent a foggy night on the sprawling base in a simple room with limited heating, sharing a shower bloc and latrine with soldiers, before heading into a breakfast meeting with British commanders.

The prime minister inspected new military hardware, including drones, that London has dispatched to Afghanistan in a bid to counter controversy over alleged supply shortages, and offered the troops his Christmas greetings.

"The combined effort of allied forces with the Afghan government is the way we will defeat the insurgency, the way we will stop Al-Qaeda having any space to operate in Afghanistan," he told a news conference with Karzai.

"I think the next few months are obviously critical," Brown told reporters travelling with him.

The extra deployment, which will boost the number of British forces in Afghanistan to more than 10,000, would arrive "in the next few days", he added.

Britain is hosting a conference on Afghanistan in London on January 28, at which Karzai is expected to be set tough new targets so foreign troops can start to hand over control to Afghan soldiers and police.

Brown said equipment for the British mission, the second-largest behind the US contingent, was "improving every day" and that the number of helicopters had doubled in the last three years.

"These things are being done in a way that is calculated to weaken the Taliban and show they can't win this campaign," he said.

Karzai, who is under Western pressure to clamp down on corruption and has yet to unveil a government since being inaugurated after a re-election steeped in fraud, pledged to do "a lot more" in building an accountable administration.

"We need to have a government that is responsive to the needs of the Afghan people. That's our responsibility and we will be taking a lot more measures," the president said.

The British leader welcomed his remarks.

"Of course, people will judge what happens by results, but I think we have seen a determination on the part of President Karzai to take new action against corruption," Brown said.

He admitted it had been "a difficult year", alluding to British troop losses in Afghanistan, which at 100 in 2009 have made this the deadliest year for the country's armed forces since the 1982 Falkland's War, but said morale was high.

Officials said Brown's visit marked the first time a British prime minister had spent a night in a theatre of war in living memory.

From Kandahar he flew by helicopter to Helmand, low over desert plains to see Afghan soldier recruits being put through their paces by British trainers and being taught to use state-of-the-art bomb detectors.

British troops are based in Helmand, the heartland of opium production in Afghanistan and one of the deadliest battlegrounds in the country.

Karzai had promised to send 10,000 extra Afghan troops to Helmand for training, Brown said.

Brown described the Afghan border areas with Pakistan as "the location of choice for Al-Qaeda" and "the epicentre of global terrorism" reiterating that three quarters of terror plots discovered in Britain had roots in the area.

Separately, the head of US Central Command, General David Petraeus, said that to defeat the Taliban in Afghanistan it was also crucial that Pakistan put pressure on Taliban leaders operating in its border zone.

To make "the really significant progress in Afghanistan that will be necessary over time... it would be very helpful if additional pressure could be put (by Pakistan) on the leadership of the elements that are causing problems in Afghanistan," he told a security conference in Bahrain.