A U.S. appeals court ruled Monday that two of President George W. Bush's top aides do not have to cooperate with a congressional investigation about the firings of nine federal prosecutors in 2006.

A three-judge panel on the U.S. Court of Appeals in Washington says that time will run out on this year's congressional session before the battle between the legislative and executive branches of government can be resolved.

The ruling blocks a U.S. District Court order in July that would have forced former White House counsel Harriet Miers to testify before the House Judiciary Committee and current presidential chief of staff Josh Bolten to turn over documents.

Democrats say the firings were politically motivated.

"The present dispute is of potentially great significance for the balance of power between the legislative and executive branches," wrote the panel of judges, which included two Republicans.

But even with a speedy appeal, it is impossible that the fight will be resolved before the current congressional session ends on Jan. 3, the judges wrote.

"At that time, the 110th House of Representatives will cease to exist as a legal entity, and the subpoenas it has issued will expire," the panel said.

The judges added: "In view of the above considerations, we see no reason to set the appeal ... If the case becomes moot, we would be wasting the time of the court and the parties."

A spokesman for the House Judiciary Committee, chaired by Rep. John Conyers, a Democrat did not immediately respond to a request for comment.