By Nick Childs BBC correspondent in Washington

Mr Bush's move is very unusual

President George W Bush has agreed to appear before members of the federal commission investigating the attacks on the United States on 11 September 2001.

But he will only meet them in private and it is not clear how much of his testimony will eventually be published.

This is a highly unusual move for an incumbent president and is a concession by the White House to the commission.

Along with the publication of Mr Bush's service records in the Air National Guard, it also looks like a second effort by the administration to try to defuse an issue that has been dogging the president recently.

For now, the White House is saying no to a public appearance.

Former President Bill Clinton and his Vice-President, Al Gore, have also tentatively agreed to appear in private.

Complaints

The commission has complained about a lack of co-operation from the Bush administration.

It had been due to report at the end of May.

But this may now be delayed until after the presidential election.

Much of Mr Bush's testimony may have to remain secret because it is likely to deal with sensitive intelligence.