WASHINGTON —  President Bush (search) and Vice President Dick Cheney will appear April 29 before the commission investigating the Sept. 11 terrorist attacks (search), an official said Wednesday.

The timing of the joint, closed-door appearance was negotiated in recent days between the White House and the National Commission on Terrorist Attacks Upon the United States (search). After initially resisting, the White House said last month that Bush and Cheney would appear together before the panel.

The issue of whether the 2001 attacks might have been prevented has dragged on in an election year, raising questions about the administration's actions in the months leading up to the attacks and potentially undercutting one of Bush's political strengths, national security.