The vote came as the Senate neared completion of a bill authorizing $400.5 billion in fiscal 2004 defense programs. A vote on the overall bill was expected Thursday. The House began considering its own defense bill Wednesday.
The change in environmental laws was a victory for Democrats after setbacks on attempts to block research of two types of nuclear weapons, the Associated Press reported.
Defense Secretary Rumsfeld said the environmental vote was a mistake and that he hoped it would be changed when House-Senate negotiators work out a final a version of the bill.