Sept. 4 (Bloomberg) -- Prime Minister Gordon Brown said British troops will stay in Afghanistan until the country can protect itself and vowed to step up the training of Afghan security forces.

In a speech in London today, Brown promised an extra 20 million pounds ($33 million) to boost security in Helmand, the southern province where British solders are deployed. Britain would support an expansion of the Afghan army to 134,000 troops by the end of 2010, a year earlier than planned, he said.

“We will have succeeded when our troops are coming home because the Afghans are doing the job themselves,” Brown told an audience of academics. “The right strategy is one that completes the job, which is to enable the Afghans to take over from international forces; and to continue the essential work of denying the territory of Afghanistan as a base for terrorists.”

Brown is under mounting pressure to justify the presence of British troops in Afghanistan amid a rising death toll and reports of voting fraud in last month’s presidential elections.

Critics including the opposition Conservatives and former military officials accuse Brown of failing to provide enough helicopters and vehicles to defeat the Taliban, the radical Islamist movement that sheltered al-Qaeda until the regime was ousted by U.S.-led forces after the Sept. 11, 2001, attacks. Polls show most Britons want their troops to return home.

Resignation

Brown’s speech was overshadowed by the resignation yesterday of an aide to Defense Secretary Bob Ainsworth in protest at the government strategy in Afghanistan, where 212 U.K. service personnel have been killed since the campaign began eight years ago.

Eric Joyce, a former army major and a member of the ruling Labour Party, quit last night, calling on Brown to make it clear to the British people that the Afghanistan campaign is “time- limited.” In his resignation letter to Brown, he argued that voters would not accept for “much longer that our losses can be justified by simply referring to the risk of greater terrorism on our streets.”

“Each time I have to ask myself if we are doing the right thing by being in Afghanistan,” Brown said. “Each time I have to ask myself if we can justify sending our young men and women to fight for this cause. And my answer has always been yes.”

Brown said the NATO goal of training 134,000 soldiers by the end of 2011 should be brought forward by a year. The new target would involve doubling the rate of training to 4,000 troops a month, he said. The Afghan army is currently just under 90,000-strong.

Air Strike

NATO aircraft destroyed two tanker trucks filled with fuel after they were hijacked by insurgents in Afghanistan today. The attack left 60 people killed and dozens injured, an Afghan spokesman said.

The U.K. has more than 9,000 troops deployed in Afghanistan, the second-largest contingent after the U.S. The U.S. is pressing its allies to increase their force levels in Afghanistan. Britain sent an extra 700 soldiers to provide security during the August election, and Brown urged other countries to contribute more to the war effort.

Brown has repeatedly justified Britain’s presence in Afghanistan as necessary to contain the threat of terrorism from the Afghanistan-Pakistan border region, maintaining that three- quarters of the terrorist plots investigated by U.K. authorities have links to al-Qaeda in Pakistan.

“When the security of our country is at stake we can not walk away,” Brown said. “When the stability of this volatile region, spanning the Afghanistan-Pakistan border, has such a profound impact on the security of Britain and the rest of the international community we cannot just do nothing and leave the peoples of Pakistan and Afghanistan to struggle with these global problems on their own.”

Answering the criticism that U.K. troops do not have enough equipment to defend themselves properly, Brown argued that military spending is “going up far in excess of the increase in troop numbers.” The U.K. is buying 20 more Ridgeback mine-protected patrol vehicles over the next three months, he said.

To contact the reporter on this story: Kitty Donaldson in London at kdonaldson1@bloomberg.net

Last Updated: September 4, 2009 12:25 EDT