Defense Secretary Donald H. Rumsfeld and Homeland Security Secretary Michael Chertoff are near agreement on a plan to give the military sole authority to shoot down civilian aircraft that violate restricted airspace over Washington, a Pentagon official said yesterday.

The proposed change follows the incursion May 11 by two lost pilots who strayed into the heart of a 16-mile-radius no-fly zone over the capital, prompting evacuations of the White House, U.S. Capitol and other buildings.

Military fighter jets diverted the single-engine Cessna when it was within a minute of reaching those potential targets. In the tense seconds beforehand, however, there was confusion over whether military commanders could legally order U.S. customs aircraft trailing the plane to open fire if jets could not get there in time, authorities said.

"There are gaps and seams remaining in terms of interagency coordination," Paul McHale, assistant secretary of defense for homeland security, testified yesterday to the House Government Reform Committee, which reviewed U.S. air defenses.

"There needs to be unity of command," he said later in an interview. "The need for that . . . is recognized by Secretary Rumsfeld and Secretary Chertoff."

Repeated incursions into the restricted airspace, which extends 2,000 square miles around Washington, have raised doubts about the effectiveness of the system. Pilots have violated the airspace 3,495 times between Jan. 27, 2003, and Sunday, the Transportation Security Administration reported. Pilots entered the smaller D.C. no-fly zone 166 times and a similar ring around Camp David 137 times during that period.

Only a few pilots have been penalized, although 665 jet or helicopter intercepts have been ordered.

Rep. John L. Mica (R-Fla.), chairman of the House aviation subcommittee, said Congress is preparing legislation to increase the penalty for pilots who intentionally violate the restricted airspace from a $1,100 fine and a 90-day license suspension to up to $100,000 and a two- to five-year suspension.

Davi D'Agostino, testifying for the Government Accountability Office, Congress's audit arm, reported that nearly four years after the Sept. 11, 2001, attacks, no single agency has been given responsibility to lead air defense efforts.

"There is no leadership over, and no agency in charge of, the end-to-end process," she said. "No one's got the job of ironing out those seams and smoothing the rough edges."

The GAO urged the Defense and Homeland Security departments to give a single agency responsibility for air defense in the capital region and the nation, warning that in a crisis, debilitating gaps among seven agencies remain.

One of the gaps concerns who can shoot at a pilot or a plane. The split law enforcement and military authority in Washington airspace puts two fingers on the trigger in a terrorist scenario, authorities said. The situation did not come into play in May but is a potential risk.

Military jets and ground-to-air missile systems in the area are under the control of the North American Aerospace Defense Command. But Customs and Border Protection agents, who patrol aboard UH-60 Black Hawk helicopters, have authority as federal law enforcement officers to use lethal force if lives are threatened. Some Customs Black Hawks are armed with laser-sighted sniper rifles that can be fired at a pilot of a slow-flying intruder.

"The military chain of command is clear," delegating shoot-down authority from the president, to the secretary of defense, to combat commanders, McHale testified. "We don't want to turn the decision of the secretary of defense into an interagency discussion."

Homeland Security spokesman Brian Roehrkasse said no final decisions or changes in procedures have been made among the department's agencies or with the Defense Department.

Chertoff also met two weeks ago with Customs and Border Protection Commissioner Robert C. Bonner and the Coast Guard commandant, Adm. Thomas H. Collins, about a proposal to turn over airspace duties from Customs to the Coast Guard, two Homeland Security officials said.

Both agencies report to Homeland Security, but the Coast Guard is part of the armed forces and has both law enforcement and military duties. No final decision has been made, although both agencies are lobbying Congress for the responsibility, and the move would have budget implications.

Yesterday, McHale said the Transportation Security Administration should take leadership and administrative responsibility for securing airspace across the United States as it has in the capital region, with the military reserving shoot-down authority and control of weapons systems.