WASHINGTON, Dec. 8  The White House budget director warned on Saturday that President Bush was prepared to veto a $500 billion spending package being assembled in Congress if Democrats pushed for too much additional money for domestic programs.

Jim Nussle, the director of the Office of Management and Budget, accused Democrats of trying to tie money for combat operations in Iraq and Afghanistan to what the president considers excessive spending for federal agencies and home-state projects.

“Instead of trying to leverage troop-funding for more pork-barrel spending, Congress ought to pass responsible appropriations bills and the funding for the troops our commanders say they need to build on their battlefield success,” Mr. Nussle said.

Democratic leaders accused the White House of responding hastily to news accounts of the proposal, which is being developed behind closed doors. They said Democrats were determined to devote more resources to national needs like homeland security and law enforcement.