Sen. Chuck Hagel, considered a potential presidential candidate in 2008, said many Republican senators support the ban proposed by Sen. John McCain, R-Ariz., a prisoner of war during the Vietnam War.
The ban was approved by a 90-9 vote last month in the Senate and added to a defense spending bill. The White House has threatened a veto, but the fate of the proposal depends on House-Senate negotiations that will reconcile different versions of the spending measure. The House's does not include the ban.
Vice President Dick Cheney has lobbied Republican senators to allow an exemption for those held by the CIA if preventing an attack is at stake.
''I think the administration is making a terrible mistake in opposing John McCain's amendment on detainees and torture,'' Hagel, R-Neb., said on ''This Week'' on ABC. ''Why in the world they're doing that, I don't know.''