NEW YORK (Reuters) - Afghanistan is at risk of reverting to control by warlords and the United States of suffering a defeat in the "war on terrorism" unless Washington strengthens the Kabul government, a nongovernmental report said on Wednesday.

It recommended the Bush administration bolster President Hamid Karzai and quickly build more international support for economic, diplomatic and security reconstruction.

The report was co-sponsored by the Council on Foreign Relations and the Asia Society in New York with a task force of 60 people in the diplomatic, business and humanitarian fields. They analyzed Afghanistan since the U.S.-led invasion.

"Unless the situation improves, Afghanistan risks sliding back into the anarchy and warlordism that prevailed in the 1990s and helped give rise to the Taliban," it said, referring to the puritanical Islamist group that governed the country of 28 million from 1996 until the 2001 U.S.-led war.

"Such a reversion would have disastrous consequences for Afghanistan and would be a profound setback for the U.S. war on terrorism," said the report, "Afghanistan: Are We Losing the Peace?"

Before overthrowing the Taliban for harboring the al-Qaeda network, accused of masterminding the Sept. 11, 2001, attacks, the United States said it would make speedy efforts to help rebuild the nation. Since then, other critics have accused Washington of falling short on some of its goals.

One of the lead authors, Frank Wisner, a former U.S. ambassador to India, said U.S. credibility was on the line and if Washington "did not get it right in Afghanistan it will be a lot harder to convince others to work with us to get it right in Iraq."

PEACEKEEPING

The authors said the Bush administration policy of excluding U.S. troops from peacekeeping responsibilities outside Kabul "fails to address the growing security challenge that the Karzai government faces." They said Washington should be prepared to help fight regional leaders and warlords.

The report said the mandate of 11,000 U.S. troops in Afghanistan should include peacekeeping outside the capital, or support for an enlarged International Security Assistance Force, now 5,000 strong. It called for the disarmament of local militias and increasing the Afghan National Army to 27,000 from the target set of 9,000 by the summer of 2004.

Among other recommendations were that the United States should provide at least $1 billion in reconstruction aid for each of the next five years and rebuild the Kabul-Kandahar road by the end of 2003, as promised by President Bush.

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