WASHINGTON – Designs for many of the nation’s most sensitive advanced-weapons systems have been compromised by Chinese hackers, according to a report prepared for the Pentagon and to officials from government and the defense industry.

Among more than two dozen major weapons systems whose designs were breached were programs critical to U.S. missile defenses and combat aircraft and ships, according to a previously undisclosed section of a confidential report prepared for Pentagon leaders by the Defense Science Board.

Experts warn that the electronic intrusions gave China access to advanced technology that could accelerate the development of its weapons systems and weaken the U.S. military advantage in a future conflict.

The Defense Science Board, a senior advisory group composed of government and civilian experts, did not accuse the Chinese of stealing the designs. But senior military and industry officials with knowledge of the breaches said the vast majority were part of a widening Chinese campaign of espionage against U.S. defense contractors and government agencies.

The significance and extent of the targets help explain why the Obama administration has escalated its warnings to the Chinese government to stop what Washington sees as rampant cybertheft.

In March, the advisory panel warned in the public version of its report that the Pentagon is unprepared to counter a full-scale cyber-conflict. The list of compromised weapons designs is contained in a confidential version that was provided to The Washington Post.

Some of the weapons form the backbone of the Pentagon’s regional missile defense for Asia, Europe and the Persian Gulf. The designs included those for the advanced Patriot missile system, known as PAC-3; an Army system for shooting down ballistic missiles, known as the Terminal High Altitude Area Defense, or THAAD; and the Navy’s Aegis ballistic-missile defense system.

Also identified in the report are vital combat aircraft and ships, including the F/A-18 fighter jet, the V-22 Osprey, the Black Hawk helicopter and the Navy’s new Littoral Combat Ship, which is designed to patrol waters close to shore.

Also on the list is the most expensive weapons system ever built — the F-35 Joint Strike Fighter, which is on track to cost about $1.4 trillion. The 2007 hack of that project was reported previously.

China, which is pursuing a long-term, comprehensive strategy to modernize its military, is investing in ways to overcome the U.S. military advantage — and cyber-espionage is seen as a key tool in that effort, the Pentagon noted this month in a report to Congress on China. For the first time, the Pentagon specifically named the Chinese government and military as the culprit behind intrusions into government and other computer systems.

As the threat from Chinese cyber-espionage has grown, the administration has become more public with its concerns. In a speech in March, Thomas Donilon, the national security adviser to President Obama, urged China to control its cyber-activity. In its public criticism, the administration has avoided identifying the specific targets of hacking.

But U.S. officials said several examples were raised privately with senior Chinese government representatives in a four-hour meeting a year ago. The officials, who spoke on the condition of anonymity to describe a closed meeting, said senior U.S. defense and diplomatic officials presented the Chinese with case studies detailing the evidence of major intrusions into U.S. companies, including defense contractors.

The Chinese government insists that it does not conduct cyber-espionage on U.S. agencies or companies, and government spokesmen often complain that Beijing is a victim of U.S. cyberattacks.

Obama is expected to raise the issue when he meets with Chinese President Xi Jinping next month in California.

A spokesman for the Pentagon declined to discuss the list from the science board’s report.

The confidential list of compromised weapons system designs and technologies represents the clearest public look at what the Chinese are suspected of targeting. When the list was read to independent defense experts, they said they were shocked at the extent of the cyber-espionage and the potential for compromising U.S. defenses.

“That’s staggering,” said Mark Stokes, executive director of the Project 2049 Institute, a think tank that focuses on Asia security issues. “These are all very critical weapons systems, critical to our national security. When I hear this in totality, it’s breathtaking.”

The experts said the cybertheft creates three major problems. First, access to advanced U.S. designs gives China an immediate operational edge that could be exploited in a conflict. Second, it accelerates China’s acquisition of advanced military technology and saves billions in development costs. And third, the U.S. designs can be used to benefit China’s own defense industry. There are long-standing suspicions that China’s theft of designs for the F-35 fighter allowed Beijing to develop its version much faster.

“You’ve seen significant improvements in Chinese military capabilities through their willingness to spend, their acquisitions of advanced Russian weapons, and from their cyber-espionage campaign,” said James Lewis, a cyber-policy expert at the Center for Strategic and International Studies. “Ten years ago, I used to call the PLA [People’s Liberation Army] the world’s largest open-air military museum. I can’t say that now.”

The public version of the science board report noted that such cyber-espionage and cyber-sabotage could impose “severe consequences for U.S. forces engaged in combat.” Those consequences could include severed communication links critical to the operation of U.S. forces. Data corruption could misdirect U.S. operations. Weapons could fail to operate as intended. Planes, satellites or drones could crash, the report said.

The list in the report did not describe the extent or timing of the penetrations. Nor did it say whether the theft occurred through the computer networks of the U.S. government, defense contractors or subcontractors.

Privately, U.S. officials say that senior Pentagon officials are frustrated at the scale of cybertheft from defense contractors, who routinely handle sensitive classified data.

“In many cases, they don’t know they’ve been hacked until the FBI comes knocking on their door,” said a senior military official who was not authorized to speak on the record. “This is billions of dollars of combat advantage for China. They’ve just saved themselves 25 years of research and development. It’s nuts.”

The systems on the science board’s list are built by a variety of top defense contractors, including Boeing, Lockheed Martin, Raytheon and Northrop Grumman. None of the companies would comment about whether their systems have been breached.