Obama emphasised that the 91,000 classified documents from 2004-2009 came before he revised the military and civilian strategy and the information was already part of the public debate on how to move forward.

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

Obama outlined his strategy in December. It called for a major buildup of troops while putting greater focus on civilian efforts to boost good governance and institutions in Afghanistan.

The documents were made available by WikiLeaks, a whistle-blowing website that has drawn sharp criticism from the government for facilitating the leaking of classified material. The documents emerged Sunday.

The White House said Monday an investigation is underway to determine the source of the leak and that federal laws were violated. The Obama administration is concerned the documents made public could pose a security threat because they reveal details of operations in Afghanistan.

Much of the focus of the documents is on concerns about civilian casualties and that elements of Pakistan intelligence agency, the ISI, had collaborated with the Taliban and other militant groups behind attacks on international forces in Afghanistan.

Obama said his revised strategy was in part based on addressing the problems exposed by the documents.