TOKYO (AFP) - Almost 30 donor countries were due to meet in Japan on Friday to raise what the World Bank hopes will be four to six billion dollars in aid pledges for poor and violence-torn Pakistan.

The World Bank and Japan are co-hosting the aid conference for the cash-strapped, politically volatile and nuclear-armed South Asian country, which shares a long and porous border with war-torn Afghanistan.

Japan's Prime Minister Taro Aso has promised up to one billion dollars.

US President Barack Obama has thrown his support behind a bill before Congress to pump 1.5 billion dollars a year into Pakistan for at least five years to build schools and infrastructure that can nurture democracy.

The World Bank has said it expects total loan and grant aid pledges of four billion to six billion dollars when 27 countries and 16 organizations attend the one-day conference and a "Friends of Pakistan" meeting.

Pakistan's President Asif Ali Zardari was set to attend the meeting, along with US envoy Richard Holbrooke, Obama's chief point man on both Afghanistan and Pakistan, and Iran's Foreign Minister Manouchehr Mottaki.

Washington has put Pakistan at the heart of the fight against Al-Qaeda and Obama has unveiled a sweeping new strategy to turn around the Afghan war and defeat Islamist militants on both sides of the border.

Leading members of the Al-Qaeda movement -- including its leader Osama bin Laden -- are widely believed to be holed up in Pakistan's lawless tribal areas near the Afghanistan border.

Zardari stressed on the eve of the conference that his government is determined to fight Islamic militants but said it needed a "massive" aid drive similar to the US Marshall Plan for post-World War II Europe.

"We are determined to fight militancy to the end and will never permit the extremists to dictate their agenda on the people through guns and bullets," he wrote in the English-language daily Japan Times on Thursday.

"Pakistan alone cannot bear the huge social and economic burden of this war," the president wrote. "Clearly we need massive international assistance.

"Pakistan needs a sort of Marshall Plan to address the issues raised in the fight against militancy."

Economists say 40 percent of Pakistan's 160 million people live on one dollar a day or less. The government puts the figure at 33 percent.

Since the September 11, 2001 attacks -- which led the United States to invade Afghanistan and make Pakistan its regional strategic ally -- Islamabad has spent about 35 billion dollars on fighting extremists, Zardari wrote.

Extremist attacks in Pakistan have killed more than 1,700 people since troops besieged gunmen holed up in a radical mosque in Islamabad in July 2007.

On Wednesday a suicide bomber blew up a vehicle packed with explosives at a police checkpoint in northwest Pakistan, killing 18 police and civilians.