The budget bill was passed unanimously by the Senate, just three days after it gained approval in a 394-26 vote in the House of Representatives.
In contrast to the climate that existed when the bill was first taken up earlier this month, when the Democrats clamoured for Defence Secretary Donald Rumsfeld's resignation, the budget did not generate debate in Friday's session.
The US$70 billion for Iraq and Afghanistan is a down payment on war costs the White House has estimated will hit US$110 billion for the budget year beginning October 1.
Congress has now approved US$507 billion for Iraq, Afghanistan and heightened security at overseas military bases since the September 11th, 2001 attacks.
The growing price tag of the Iraq conflict is partly driven by the need to repair and replace military equipment worn out in harsh, dusty conditions in Iraq and Afghanistan or destroyed in battle.
The defence budget bill is the first of 11 spending bills to clear Congress for the new budget year. It is now on its way to the White House for President George W Bush's signature.