PARIS — The United States, Europe and more than 60 other countries and international institutions offered about $20 billion in aid for Afghanistan as part of a big donors conference in Paris Thursday. But amid the public pledges of support, officials were fretting over whether the Afghan government is doing all that it can to make sure the money goes to rebuilding and not into the pockets of the country's warlords and corrupt government officials.

More than half of the pledge total came from a previous commitment by the United States to provide $10.2 billion. Britain pledged $1.2 billion over the next five years.

Some of the largest increases came from France and Japan. President Nicolas Sarkozy of France promised to "more than double" French aid, to more than $165 million over the next two years, French officials said; and Japan also doubled its aid, to $550 million. Germany offered more than $600 million over the next two years.

U.S. first lady Laura Bush called on international donors to "reaffirm our commitment" to the country's success and showed slides from her recent trip to the assembled leaders, which included President Hamid Karzai of Afghanistan and U.N. Secretary-General Ban Ki-moon.

U.S. officials at the conference expressed overall satisfaction with the offerings. But an undercurrent of frustration ran throughout the meeting. U.N., European and even Bush administration officials have been voicing increased frustration with Karzai over his inability to crack down on corruption and drug trafficking in Afghanistan.

Karzai asked for $50 billion to finance a five-year development plan intended to revive Afghanistan's decrepit farming sector, promote economic development and develop and diversify the economy away from its heavy reliance on opium.

But U.S. and European officials privately expressed particular frustration over the Afghan president's refusal to arrest drug lords who are running the country's opium trade, which many international analysts say the Taliban have used to fuel their comeback.

Even the public comments at Thursday's meeting reflected that frustration. Ban said that while donors should increase aid to Afghanistan, they should also demand better standards from the Afghan government. "Every act of corruption is a deliberate act by someone in a position of authority," he said. He called for active measures to be taken to fight corruption and make sure that the money went to those who actually needed it.