The Vietnam-era memos released late on Wednesday add new dimensions to the bare-bones explanation of Bush's aides over the years that he was suspended simply because he decided to skip his annual physical exam.

The exam was scheduled during a year in which Bush left Texas, where he had been flying fighter jets, to work on a US Senate campaign in Alabama.

White House communications director Dan Bartlett told CBS' 60 Minutes II, which first obtained the memos, that Bush's superiors granted permission to train in Alabama in a non-flying status and that "many of the documents you have here affirm just that".

"On this date I ordered that 1st Lieutenant Bush be suspended from flight status due to failure to perform to USAF/TexANG standards and failure to meet annual physical examination ... as ordered," states a 1 August, 1972, memo by Lieutenant Colonel Jerry Killian.

Clashing opinions

A memo a year later points to turmoil among Bush's superiors over how to rate his performance because there was no "feedback" from Guard officials in 1972 and 1973 in Alabama, where Bush had been largely inactive.

"...I ordered that 1st Lieutenant Bush be suspended from flight status due to failure to perform to USAF/TexANG standards and failure to meet annual physical examination ... as ordered"

Lieutenant Colonel Jerry Killian,
1 August, 1972, memo

A third Killian memo says that Killian was concerned from the outset over Bush's plan to go to Alabama because the military had spent a substantial sum of money turning Bush into a pilot and that his National Guard duties might suffer if he went elsewhere.

"Phone call from Bush," Killian wrote in a 19 May, 1972, memo. "Discussed options of how Bush can get out of coming to drill from now through November. ... Says that he is working on another campaign for his dad. ... We talked about him getting his flight physical situation fixed... Says he will do that in Alabama if he stays in a flight status."

The memo added that Bush "has this campaign to do and other things that will follow and may not have the time. I advised him of our investment in him and his commitment".

White House explanation

The White House told CBS that Bush "met his drills then when he came back" from Alabama "and that's why he received an honourable discharge".

With national security, the war on terrorism and Iraq looming large on voters' minds, supporters of Bush and Democratic nominee John Kerry are attacking each candidate's Vietnam War records.

Senator John Kerry's war record
has been a politicised topic

Republicans have accused Kerry, a decorated Vietnam combat veteran, of fabricating the events which led to his five medals.

Democrats point to gaps in Bush's stateside Air National Guard service in 1972 and 1973 to say Bush shirked his duty.

Asked about Killian's memo which gives two reasons for Bush's suspension, Bartlett told CBS, "That might be official language."

'Physical not needed'

Bartlett said "the records have been clear for years that President Bush did not take a physical because he did not need to take a physical because, obviously, the choice was that he was going to be performing in a different capacity".

Asked about Killian's statement in a memo about the military's investment in Bush, Bartlett told CBS: "For anybody to try to interpret or presume they know what somebody who is now dead was thinking in any of these memos, I think is very difficult to do."

On Tuesday, the Defence Department released more than two dozen pages of records about Bush and his former Texas unit. They showed Bush flew for 336 hours in military jets after his flight training and ranked in the middle of his class.

Pentagon officials said they discovered the documents released on Tuesday while performing a more comprehensive search "out of an abundance of caution" in response to a Freedom of Information Act lawsuit by The Associated Press.