The Republican chairman of a House panel investigating the response to Hurricane Katrina threatened Wednesday to issue subpoenas for documents if the White House and other agencies don't provide them by Nov. 18.

Rep. Tom Davis of Virginia made the commitment after a Louisiana Democrat, Charlie Melancon, pointed out the panel still hadn't seen some documents it requested more than a month ago. The original request pertains to the White House, Department of Homeland Security, Department of Health and Human Services and the states of Alabama, Louisiana and Mississippi.

Davis said there had been a significant response from the White House, Alabama and Mississippi and that the Department of Homeland Security had assured him it would provide documents within a week.

"This is progress, but it's not enough," Davis said.

"Lack of compliance is hindering the investigation," Melancon said.

The committee made its initial request in late September and set a due date for Oct. 4. Some of those documents have been provided, including a few pertaining to budget issues and e-mails between former Federal Emergency Management Agency chief Michael Brown and Homeland Security headquarters.

However, Melancon said most of the key documents are missing — including anything involving Homeland Security Michael Chertoff, Defense Secretary Donald Rumsfeld and correspondence between federal agencies. Louisiana has indicated it will provide documents but has requested an extension, Melancon's office said.