Bush momentarily switched the names of his two greatest nemeses in a news conference at the White House where he was defending his decision to authorise eavesdropping on Americans suspected of links with al Qaeda and other organisations in the U.S. war on terrorism.

"In the late 1990s, our government was following Osama bin Laden because he was using a certain type of telephone and then the fact that we were following Osama bin Laden because he was using a certain type of telephone made it into the press as the result of a leak," Bush said.

"And guess what happened. Saddam ...Osama bin Laden changed his behaviour. He began to change how he communicated. We're at war. And we must protect America's secrets."

The Bush administration sought to convince Americans before the invasion of Iraq that Saddam Hussein's government had links to bin Laden's al Qaeda. No such links have been proven.

The US National Security Agency(NSA) first began to conduct warrantless eavesdropping on telephone calls and e-mail messages between the United States and Afghanistan in the immediate aftermath of the Sept. 11, 2001, attacks, The New York Times reported Sunday.

The NSA's surveillance of telecommunications between the United States and Afghanistan started months before President George W. Bush officially authorized a broader version of the agency's special domestic collection program, current and former government officials were quoted as saying.

The agency operation included eavesdropping on communications between Americans and other individuals in the United States and people in Afghanistan without the court-approved search warrants that are normally required for such domestic intelligence activities.

After the Sept. 11 attacks, the Bush administration and senior American intelligence officials quickly decided that the existing laws and regulations restricting the government's ability to monitor American communications were too rigid to permit quick and flexible access to international calls and e-mail traffic involving terrorism suspects, the report said.

In the days after the attacks, the Central Intelligence Agency determined that al Qaeda, which had found a haven in Afghanistan, was responsible. Congress quickly passed a resolution authorizing the president to conduct a war on terrorism, and the security agency was secretly ordered to begin conducting comprehensive coverage of all communications into and out of Afghanistan, including those to and from the United States, current and former officials said.

It could not be learned whether Bush issued a formal written order authorizing the early surveillance of communications between the United States and Afghanistan that was later superseded by the broader order, according to the report.