LONDON (Reuters) -- Afghanistan will receive promises of economic and military support from more than 50 countries at a conference in London on Tuesday in return for pledges to fight corruption and the illegal opium trade.

Four years after the U.S.-backed campaign which ousted the Taliban, Afghanistan remains one of the world's poorest countries and security remains a major obstacle to development.

A Taliban leader condemned the gathering as an "American drama and stage show" and warned that the Taliban would continue its suicide and other attacks on Western forces in the country.

The international community will commit itself to helping Afghanistan achieve peace and stability at the two-day conference, chaired by Afghan President Hamid Karzai, British Prime Minister Tony Blair and UN Secretary-General Kofi Annan.

U.S. Secretary of State Condoleezza Rice said the aim was to help the Central Asian country stand "on its own feet".

"Afghanistan is a wonderful success story but we recognize there's a long road ahead," she said.

But a former Afghan minister said billions of dollars of aid that have poured into the country have done little to improve people's lives, and sweeping personnel changes in government and aid agencies are needed.

"There is minimum improvement in the lives of the ordinary people," and much aid money has been wasted, former Planning Minister Ramazan Bashardost told a Kabul news conference.

"The people are asking themselves 'if these billions of dollars have been donated, which of our pains have they remedied, what ointment has been put on our wounds'," he said. Mullah Abdullah Akhund, deputy to Taliban leader Mullah Mohammad Omar and a former Taliban defense minister, said Afghans "should not attach big hopes to the London conference," which he said was an "American drama and stage show."

"In Afghanistan, armed jihadi and suicide attacks against America, Britain and their agents will continue," he told Reuters by satellite telephone from an undisclosed location. ------------------------------ Constitution and Parliament

The United States helped anti-Taliban Afghan forces oust the hardline Islamic militants in 2001 after the Taliban refused to hand over Al-Qaeda leaders responsible for the Sept. 11, 2001 attacks that killed nearly 3,000 people in New York and Washington.

The country now has a constitution, an elected president and a Parliament despite violence in the south and east where 18,000 U.S. troops are helping government forces fight insurgents.

Officials have blamed Taliban and Al-Qaeda militants for a string of attacks, including 13 suicide blasts, since November.

NATO is preparing to boost its forces in Afghanistan to 18,000 from 9,000 and expand into the dangerous south while the United States cuts its troop levels. Britain announced last week it will send an additional 3,300 troops.

The gathering, attended by 51 countries, 17 observers and 12 international bodies, is not a pledging conference but British officials say they expect some nations to offer more aid, especially to a fund to fight illegal drugs.

Afghanistan has received more than $15 billion in international development aid since 2001, according to Britain, and the conference will suggest ways of using the aid more effectively by giving more directly to the government.

The UN's World Food Program urged donors to focus on the poor in a land where half the children are malnourished.

"Peace is still not assured, and we must remember there are still millions of extremely poor and hungry people who need help," said Charles Vincent, WFP's Afghanistan director.

Delegates are looking for assurances that Kabul will tackle corruption and its illegal narcotics trade.

Afghanistan is the world's biggest source of illicit opium and its refined heroin accounts for about 87 percent of global supply. Many farmers depend on revenue from the drug.

Karzai told BBC radio on Tuesday it would take 10 to 15 years to develop alternative sources of income for farmers and eliminate opium from Afghanistan.