WASHINGTON — An increasingly confrontational President Bush today vetoed a bill authorizing hundreds of popular water projects even though lawmakers can count enough votes to override him.

Mr. Bush brushed aside significant objections from Capitol Hill, even from Republicans, in thwarting legislation that provides money for projects like repairing hurricane damage, restoring wetlands, and preventing flooding in communities across the nation.

This level of opposition virtually assured that Mr. Bush would have a veto overridden for the first time in his presidency. He has used the veto very sparingly for most of the time he has been in office, but has made more use of it recently.

“When we override this irresponsible veto, perhaps the president will finally recognize that Congress is an equal branch of government and reconsider his many other reckless veto threats,” the Senate majority leader, Harry Reid, Democrat of Nevada, said.

“More than two years after failing to respond to the devastation and destruction of Hurricane Katrina, he is refusing to fund important projects guided by the Army Corps of Engineers that are essential to protecting the people of the Gulf Coast region.”

The $23 billion water bill passed in both chambers of Congress by well more than the two-thirds majority needed to vacate a veto and make the bill law.

Mr. Bush objected to the $9 billion in projects added during negotiations between the House and Senate. He hoped that his action, even though it is sure not to hold, would cast him as a friend to conservatives who demand a tighter rein on federal spending.

But Mr. Bush never vetoed spending bills under the Republican Congress, despite budgetary increases then, too. Attempting to demonstrate fiscal toughness now, in the seventh year of his presidency, carried the risk of being criticized for doing too little, too late or as waging a transparently partisan attack against the Democrats who now run Capitol Hill.

The president took the gamble, making it part of a broader effort to more pointedly and frequently take on Democratic leaders.

The legislation originally approved by the Senate would have cost $14 billion and the House version would have totaled $15 billion. Mr. Bush and a few Republicans complained that the final version was larded with unneeded pet projects pushed by individual lawmakers — sending the overall cost of the bill much higher.

“Only in Washington could the House take a $14 billion bill into a conference with the Senate’s $15 billion bill and emerge with a compromise that costs taxpayers over $23 billion,” a White House press secretary, Dana Perino, said.

She also said Mr. Bush vetoed the bill because it is “fiscally irresponsible” and falls outside the scope of the Army Corps’ mission.

Critics noted that the bill piles more work on the Army Corps of Engineers, which already has a backlog of $58 billion worth of projects and an annual budget of only about $2 billion to address them.

If Mr. Bush is overridden, the measure would give a green light to projects in virtually every state. It only authorizes the projects; the actual funding must be approved separately.