Democrats have more than the two-thirds majority votes in both chambers of Congress needed to override Bush if he vetoes the bill. The Senate passed it on Sept. 24 by a vote of 81-12; the House passed it Aug. 1 by a vote of 381-40.

An override would mark the first such loss for Bush and could cast him in a more politically vulnerable light.

"This congressionally approved bill authorizes more than 200 projects to protect lives and livelihoods in our communities from the devastating impacts of flooding by building and repairing floodwalls and levees, as well as by restoring wetlands that absorb floodwaters," House Speaker Nancy Pelosi, D-Calif., and four other top House Democrats wrote Bush in a letter Friday urging him to sign the bill they sent to him on Tuesday.

The bill funds work to restore the hurricane-ravaged Louisiana coast and Florida's Everglades, projects the Bush administration supports. But the president threatened a veto after the bill's anticipated cost ballooned by $9 billion as projects were added in negotiations between the House and Senate.

The legislation authorizes $3.6 billion for major wetlands and other coastal restoration, flood control and dredging projects for Louisiana, a state where coastal erosion and storms have resulted in the disappearance of huge areas of land.