Defence Secretary Donald H Rumsfeld's secret memo to President George W Bush offering new approaches in Iraq was developed over a period of weeks, according to a newly declassified cover letter.
The letter, obtained on Monday, also said Rumsfeld had instructed Army General John Abizaid, the top commander for US forces in the Middle East, to assemble his own group "some time ago" to consider new approaches in Iraq, "since war plans of this type" are the responsibility of Abizaid's command.
There has been no public disclosure of recommendations from the Abizaid group.
The letter, addressed to Bush, Vice President Dick Cheney and Stephen Hadley, the president's national security advisor, was transmitted with the memo and dated November 6, two days before Rumsfeld resigned.
The cover letter was declassified on Monday by Rumsfeld.
The options paper remains classified secret, although its contents were published in full by The New York Times on Sunday and authenticated by Pentagon press secretary Eric Ruff.
Some in Congress have questioned the timing of Rumsfeld's memo outlining an "illustrative new course of action" in Iraq, suggesting that it came to light as a way of defending Rumsfeld's reputation as he was about to leave office.
He resigned on November 8, a day after congressional elections gave Democrats control of both the House of Representatives and the Senate. The management of the Iraq war was considered a principal consideration for the voters.