Sirens blared, cannons boomed, bands played, and balloons filled the air as the Navy and one of the country's largest military contractors today christened the United States' fifth nuclear-powered aircraft carrier amid partisan rhetoric that scored Democrat Walter F. Mondale's opposition to the ship.

More than 11,000 Navy families, shipyard workers and spectators cheered as the $2.7 billion Theodore Roosevelt was launched at the Newport News Shipbuilding and Drydock Co. yard 10 days before the presidential election.

Virginia Sen. John W. Warner, a Republican seeking reelection Nov. 6, and Navy Secretary John F. Lehman Jr. used the event to extol the virtues of the president whose name the ship bears and to criticize the Carter-Mondale White House for opposing its construction.

Lehman said that construction of the 1,092-foot carrier, which is nearly as long as the Empire State Building is tall, "makes a dramatic break in a decade of deceptive dreaming in defense matters."

Lehman, considered the architect of President Reagan's 600-ship Navy, said that the Roosevelt was "born of epic struggle," and he noted that Mondale, while vice president, led the fight to stop the carrier in 1979.

Lehman said that Carter decided not to veto appropriations for the Roosevelt in 1980, in part because of actions by Warner, a former Navy secretary. Warner, Lehman said, is "destined to become one of the giants" of national security.

Warner also attacked "President Carter and Vice President Mondale" for vetoing funds for the carrier.

"America is strong again," Warner said. "We have regained the ability to speak softly and convincingly."

By contrast, Defense Secretary Caspar W. Weinberger, the principal speaker, was low-key. He spoke only generally of previous administrations when he said that "a decade of neglect of the very substance of our defenses" had "stretched thin" American seapower.

The Roosevelt is a symbol of the Reagan administration's commitment to increase the number of aircraft carriers from 12 to 15 and of its buildup of surface ships.

Critics say the crippling of the British destroyer Sheffield by a French-designed missile in the 1982 war with Argentina over the Falklands showed the vulnerability of surface ships. Navy officials say carriers' sophisticated warning systems, and their deployment with numerous other craft in "carrier groups," make them relatively safe.

Reagan has used aircraft carriers in potential hot spots from the coast of Central America to the Mediterranean Sea off Beirut to demonstrate American military might.

Ship launchings frequently are partisan affairs, and today's was no different. Also on the dais was Rep. Herbert Bateman (R-Va.), running for reelection in a hotly contested race.

Newport News Shipbuilding spokesmen said they did not think the event was scheduled to coincide with the election, but rather to fall on the 126th anniversary of Roosevelt's birthday.

More than 10,000 workers at the shipyard, Virginia's largest private employer, worked on the Roosevelt. People in the crowd, many wearing Reagan-Bush buttons, expressed excitement and a patriotic tingling.

"I thought it was very exciting," said Donna Williams of Newport News, a Navy wife who was carrying three American flags. "It makes you appreciate your country, and it makes us Navy people proud."

Barbara Lehman of McLean, the Navy secretary's wife, christened the ship by smashing a bottle of champagne on its giant hull. The band struck up "Anchors Aweigh," 65,000 balloons were released, and four F14s flew overhead.

Tugboats then towed the 24-story carrier 17 blocks to another berth, where work will begin on outfitting the vessel's propulsion system. The Navy is expected to commission the ship in 1986.

The carrier, decorated in red, white and blue bunting and flags, was an imposing sight. Almost 100 aircraft will be able to take off from its 4 1/2-acre flight deck. It will have a crew of 6,200.

Boy Scouts handed out American flags and pins with pictures of Teddy Roosevelt, and VIPs were treated to small teddy bears, named in honor of the president.