WASHINGTON, March 21 — A House Judiciary subcommittee today authorized subpoenas for Karl Rove, President Bush's political adviser, and other senior White House officials in the investigation into the firing of eight United States attorneys.

Democrats said the subpoenas, approved on a voice vote of the panel, would not be issued immediately but could provide leverage for Congress in trying to win the testimony of the aides being sought.

"We have worked toward voluntary cooperation on this investigation, but we must prepare for the possibility that the Justice Department and White House will continue to hide the truth," said Representative Linda Sanchez of California, chairwoman of the subcommittee on commercial and administrative law.

Republicans on the subcommittee said they did not dispute the power of Congress to call the officials, but said the action was premature and smacked of politics.

"The only purpose of the subpoenas is to the fan the flames and photo ops of partisan controversy," said Representative Chris Cannon of Utah, the senior Republican on the subcommittee.

President Bush and Congress appear to be headed toward a constitutional showdown over the demands for testimony and for internal White House documents.

Under growing political pressure, the White House had offered to allow private interviews with Mr. Rove, Harriet E. Miers, the former White House counsel; and two other officials. It also offered to provide access to e-mail messages and other communications about the dismissals, but not those between White House officials.

Democrats promptly rejected the offer, which specified that the officials would not testify under oath, that there would be no transcript and that Congress would not subsequently subpoena them.