Following talk of Congress potentially trying to add back in spending for unwanted defense acquisitions, Secretary of Defense Robert Gates sent a letter threatening a veto if "dud" programs were added back into the final conference bill. See the coverage on Danger Room:

“The defense spending bill should not provide funding for weapons that are not working or are no longer needed,” he wrote to Rep. John Murtha, the chairman of the House appropriations defense subcommittee and long-time mouthpiece for the military-industrial complex’s worst inclinations.

See the full letter here.