Defending his strategy for the unpopular war after the unauthorized release of some 91,000 classified reports, Obama insisted the leak underscored the need to stick to his approach and he urged Congress to approve critical additional funds for the war effort.

"While I'm concerned about the disclosure of sensitive information from the battlefield that could potentially jeopardize individuals or operations, the fact is, these documents don't reveal any issues that haven't already informed our public debate on Afghanistan," Obama told reporters after a meeting with congressional leaders.

The documents, made public by the whistle-blowing website WikiLeaks, detail allegations that US forces sought to cover up civilian deaths as well as US concern that Pakistan secretly aided Taleban militants even as it took billions of dollars in US aid.

Obama said the reports "point to the same challenges that led me to conduct an extensive review of our policy last fall."

"For seven years, we failed to implement a strategy adequate to the challenge in this region, the region from which the 9/11 attacks were waged and other attacks against the United States and our friends and allies have been planned," Obama said.

The US Army opened a criminal probe Tuesday into the leak, the Pentagon said, naming a jailed soldier as a "person of interest." Bradley Manning, a 22-year-old private charged in an earlier leak to WikiLeaks, was under renewed scrutiny in the latest release to the same whistleblowers' website, Pentagon press secretary Geoff Morrell said.

Afghanistan's national security adviser, meanwhile, called on the West to review policy toward Pakistan. Rangeen Dadfar Spanta, President Hamid Karzai's national security adviser, took issue with US aid to Pakistan, which last year secured a $7.5 billion nonmilitary package from Congress spread over the next five years.

"It's not justifiable for Afghans to see a country given 11 billion dollars in reconstruction aid and to support its security forces, and then see those same forces training terrorists," said Spanta.

"At least we Afghan politicians are not able to explain this to the Afghan people," he said, calling on US and NATO troops to deal with insurgents before they infiltrated Afghanistan from their sanctuaries in Pakistan.

Karzai has ordered Spanta and Afghan Foreign Minister Zalmai Rasoul to "study the leaked US documents," a statement from the president's office said.