MACDILL AIR FORCE BASE, Florida (CNN) -- Four years after declaring victory in Iraq in a much-ballyhooed speech from the deck of an aircraft carrier, President Bush said Tuesday a U.S. failure in the 4-year-old war "should be unacceptable to the civilized world."

The White House marked the anniversary by accusing congressional Democrats of using the date to present Bush with a $124 billion war-spending bill that calls for the withdrawal of American combat troops.

Bush has vowed to veto the bill. Speaking to U.S. and allied military officers at U.S. Central Command headquarters outside Tampa, he said the current push to pacify Baghdad and the western province of Anbar has produced progress, but will need several months to succeed.

"Coalition forces have captured a number of key terrorist leaders who are providing information about how al Qaeda operates in Iraq," he said. "They stopped a car bomb network, that had killed many citizens of Baghdad, and destroyed major car bomb factories. There has been a decline in sectarian violence and in some areas of the capital Iraqis are returning to their neighborhoods with an increased feeling of security."