Hours after a commercial plane struck the Pentagon on September 11 2001 the US defence secretary, Donald Rumsfeld, was issuing rapid orders to his aides to look for evidence of Iraqi involvement, according to notes taken by one of them.

"Hard to get good case. Need to move swiftly," the notes say. "Near term target needs - go massive - sweep it all up, things related and not."

The handwritten notes, with some parts blanked out, were declassified this month in response to a request by a law student and blogger, Thad Anderson, under the US Freedom of Information Act. Anderson has posted them on his blog at outragedmoderates.org.

The Pentagon confirmed the notes had been taken by Stephen Cambone, now undersecretary of defence for intelligence and then a senior policy official. "His notes were fulfilling his role as a plans guy," said a spokesman, Greg Hicks.

"He was responsible for crisis planning, and he was with the secretary in that role that afternoon."

The report said: "On the afternoon of 9/11, according to contemporaneous notes, Secretary Rumsfeld instructed General Myers [the chairman of the joint chiefs of staff] to obtain quickly as much information as possible. The notes indicate that he also told Myers that he was not simply interested in striking empty training sites. He thought the US response should consider a wide range of options.

"The secretary said his instinct was to hit Saddam Hussein at the same time, not only Bin Laden. Secretary Rumsfeld later explained that at the time he had been considering either one of them, or perhaps someone else, as the responsible party."

The actual notes suggest a focus on Saddam. "Best info fast. Judge whether good enough [to] hit SH at same time - not only UBL [Pentagon shorthand for Usama/Osama bin Laden]," the notes say. "Tasks. Jim Haynes [Pentagon lawyer] to talk with PW [probably Paul Wolfowitz, then Mr Rumsfeld's deputy] for additional support ... connection with UBL."

Mr Wolfowitz, now the head of the World Bank, advocated regime change in Iraq before 2001. But, according to an account of the days after September 11 in Bob Woodward's book Plan of Attack, a decision was taken to put off consideration of an attack on Iraq until after the Taliban had been toppled in Afghanistan.

But these notes confirm that Baghdad was in the Pentagon's sights almost as soon as the hijackers struck.