Intelligence agencies in China and Russia gained access to highly classified U.S. intelligence and military information contained on electronic media held by renegade former National Security Agency (NSA) contractor Edward Snowden, according to U.S. officials.

The exact compromise of the secret data held on Snowden’s laptop computers remains unknown but is the subject of an ongoing damage assessment within NSA and other intelligence agencies, said officials familiar with the case.

One of the biggest fears about the compromise is whether Snowden, an NSA contractor and former CIA technician who hacked into classified intelligence networks, gained access to new U.S. nuclear war plans, the officials said.

The nuclear war plans, among the most closely guarded U.S. secrets, were recently modified as a result of President Barack Obama’s shift in U.S. nuclear strategy.

The president last week signed new guidance for the Pentagon limiting the use of nuclear weapons in U.S. planning and strategy. The shift is the first step in the president’s plan to cut deployed nuclear weapons by one-third to about 1,000 warheads. That plan was announced in Berlin June 19.

"The Chinese already have everything Snowden had," said one official who said there were intelligence reports indicating Chinese Ministry of State Security (MSS) agents have been in contact with Snowden during his month-long stay in Hong Kong.

Snowden had four laptop computers while in Hong Kong that contained what he asserted were thousands of classified documents he gathered while working at NSA and other intelligence agencies. He is known to have used encryption for his communications with news reporters.

Asked at a Chinese Foreign Ministry press briefing if Snowden was a spy for China, spokesman Hua Chunying said: "This is utter nonsense and is extremely irresponsible."

The timing of Snowden’s disclosures of NSA surveillance and cyber reconnaissance of China—he first went public days before the summit between Obama and Chinese President Xi Jinping—raised questions about whether he was under Chinese control. His disclosures of NSA’s PRISM program and other highly classified electronic spying muted U.S. efforts to press China on its cyber attacks.

NSA Director Gen. Keith Alexander said Sunday: "What Snowden has revealed has caused irreversible and significant damage to our country and to our allies." He did not elaborate.

Alexander said during earlier congressional testimony that Snowden, as a computer network administrator, had access to NSA "web forums" that limited his access to collected intelligence.

Snowden said in an online chat hosted by the Guardian newspaper June 17 that "I did not reveal any U.S. operations against legitimate military targets."

The comment suggests Snowden had access to military secrets but had not at that point in his defection disclosed them.

U.S. officials believe Russian intelligence delayed Snowden’s departure from Moscow in order to question him about NSA programs targeted on Russia.

Snowden remained in Moscow on Tuesday and U.S. officials said it is "highly likely" that several laptop computer carried by Snowden were "imaged" by Russian intelligence, which would have access to everything carried by the former NSA contractor.

Russian President Vladimir Putin told reporters in Finland on Tuesday that Snowden "is a transit passenger in the transit zone and is still there now. … Mr. Snowden is a free man. The sooner he selects his final destination point, the better both for us and for himself."

A former NSA official said Snowden’s claims of access to NSA surveillance programs appeared to be exaggerated. The former official said that most of what he has disclosed so far has been reported in the public domain in the past.

However, Snowden provided the Guardian and Washington Post with classified documents that indicated he was able to gain unauthorized entry into tightly guarded classified information systems. The documents included a presidential order on cyber warfare, PowerPoint slides from secret briefings on Internet data surveillance, and the first ever leak of a Foreign Intelligence Surveillance Act (FISA) court order for data records.

John Bolton, former undersecretary of state for international security, said the Snowden case could be a national security disaster.

"Many in the U.S. intelligence community fear the worst, namely that both Russia and China will have had full access to whatever documents Snowden has, plus whatever he has on the NSA laptop computers he took with him, plus whatever he told their respective authorities in debriefings," Bolton told the Washington Free Beacon.

"All of this raises the question how much help he had either from his media handlers, WikiLeaks, or other sources of support."

Bolton said earlier on Fox News Channel that the administration should take punitive action against China and Russia for not assisting in the repatriation of Snowden.

Snowden told the South China Morning Post in an interview that he initially took the position with the NSA contractor Booz Allen to gain access to intelligence he could take with him to expose what he believes is illicit U.S. electronic surveillance.

"Though he has posed as a lone wolf, you have to wonder if he had assistance or help since he has been in the United States," Bolton said. "We know since he has been in Hong Kong he had help and financial assistance from WikiLeaks. The real question is did he have help before he departed?"

Bolton said intelligence provided by someone in Snowden’s position could be used to counter U.S. electronic spying and "that’s very damaging."

Sen. John McCain (R., Ariz.) said on CNBC that the failure of cooperation from both Moscow and Beijing was due to the Obama administration’s weakness.

"It means that for five years now, we have sent a signal to the world that we're ‘leading from behind,’ that we are impotent, that we don't act when we say that we're going to," McCain said.

Alexander, the NSA director, said investigators at NSA and the FBI are working to figure out how the computer administrator was able to gain access to computer systems that are normally restricted to officials who have been granted access by a special "certificate" designed to prevent such unauthorized access.

Snowden’s representative in Hong Kong, legislator Albert Ho, told news outlets a Chinese official on Friday told Snowden to leave Hong Kong and that his departure would not be delayed.

Ho also told the Standard newspaper that Snowden stayed in two different hideouts after he left the Mira hotel after giving a videotape interview to the Guardian.

The disclosure that Ho knew Snowden’s location also indicates that Chinese authorities were aware of his location, the U.S. officials said.

Snowden’s departure was a snub from Beijing to the United States. Senior Obama administration officials made several requests to both Beijing and Hong Kong authorities to detain Snowden so he could be extradited to face charges on disclosing classified information.

The Obama administration expressed surprise that both China and Russia ignored requests to detain and extradite Snowden.

"It would be very disappointing if he was willfully allowed to board an airplane" in Hong Kong for travel to Moscow, Secretary of State John Kerry said Monday during a visit to India.

Kerry also said he would be "deeply troubled" if Russia and China assisted Snowden’s travel and ignored U.S. requests for assistance in capturing him.

"And there would be, without any question, some effect and impact on the relationship and consequences," Kerry said.

For relations with China, Snowden’s escape from Hong Kong undermined U.S. efforts to build trust with Beijing, White House spokesman Jay Carney said.

"The Chinese have emphasized the importance of building mutual trust, and we think that they have dealt that effort a serious setback," Carney said. "If we cannot count on them to honor their legal extradition obligations, then there is a problem."

The Obama administration’s efforts over the past five years to reset relations with Russia also may be undermined by Moscow’s handling of the Snowden case.

At the State Department on Tuesday, spokesman Patrick Ventrell said, "We do agree with President Putin that we do not want the issue to negatively affect the bilateral relationship."

"And so while we do not have an extradition treaty with Russia and do not expect that Mr. Snowden be formally extradited, we do believe there is a basis for law enforcement cooperation to expel Mr. Snowden based on the charges against him and the status of his travel documents," Ventrell said.

Russian nationalist political figure Vladimir Zhirinovsky, sent a tweet on Monday that said Russia should seek to exchange Snowden for imprisoned Russian arms dealer Viktor Bout and convicted drug pilot Konstantin Yaroshenko.

The newspaper Izvestiya reported Monday that "Snowden's flight to Moscow was coordinated with the Russian authorities and security services and despite the fact that his disclosures are not a sensation for specialists, representatives of the Main Intelligence Directorate, the GRU military intelligence service and Federal Security Service (FSB) will absolutely meet and converse with him."

Michelle Van Cleave, the former national counterintelligence executive, said the Snowden case is a slowly unraveling nightmare for U.S. counterintelligence officials.

"At this stage, there is no telling whether or not Snowden acted alone or what all he compromised," Van Cleave told the Free Beacon.

"Whether or not there are audit trails for IT administrators, we can only guess. If not, there may be no way of bounding the potential damage here."

Van Cleave said damage will be revealed when sources and methods of intelligence "go dark, as they surely will, and we will be hard pressed to rule out Snowden as the possible cause."

"In other words, other spies still in place will be able to continue to operate under the cover that Snowden’s espionage provides," she said. "And since we don’t know what secrets may have been lost, we won’t know what or who may now be at risk. That uncertainty alone is an intelligence bonanza for our adversaries."

Kenneth deGraffenreid, a former National Security Council staff intelligence director during the Reagan administration, said the Snowden case is similar to the Bradley Manning case, where a junior enlisted soldier stole hundreds of thousands of secret documents and gave them to the anti-secrecy group WikiLeaks.

"This is yet another rcase where a person who is a low-level ne’er-do-well is able to compromise the most sensitive intelligence," he said in an interview.

U.S. security was supposed to be improved by the shift from paper documents to digital information systems, but obviously it was not, deGraffenreid said.

For example, Foreign Intelligence Surveillance Act documents are "extremely" closely held within government, yet Snowden was able to access a FISA court order.

DeGraffenreid said Snowden, along with Manning and Wikileaks founder Julian Assange, appear to be part of the "international, anti-American left" movement.

"If there are 30-year-old radicalized, narcissistic kids who can get to the core of American intelligence secrets, and walk them out of the building and fly to China with them, we have a very serious security problem that has to be fixed," he said.