The U.S. Defense Department's F-35 program office said the latest documents released by the German magazine Der Spiegel "rehashed" a previously disclosed and reported 2010 incident, which it said compromised only non-classified data about the new warplane being built by Lockheed Martin Corp (>> Lockheed Martin Corporation).

"Classified F-35 information is protected and remains secure," the program office said in a statement released Tuesday. It said all potential cyber-attacks were taken seriously and the 2010 incident was not expected to cause any negative impact to the program.

In a statement, the Pentagon's F-35 program office said it remained "ever vigilant" about potential cyber attacks. It said the Pentagon was taking specific measures to counter evolving cyber threats against all fielded weapons systems, including the F-35.

The program office said the warplane's ability to survive cyber attacks was "foundational to the program's development, remains robustly resourced, and will continue to be a priority for the department."

China on Monday dismissed allegations that it had stolen F-35 stealth fighter plans, radar designs and engine schematics after the German magazine published documents leaked by Snowden, a former contractor with the U.S. National Security Agency.

Lockheed declined comment on the Spiegel report but said it carefully monitored and defended its computer networks against a wide range of cyber attacks and regularly shared its data with the U.S. government, public utilities and other companies.

"As a global security and aerospace company, Lockheed Martin is a target for a wide range of cyber-attacks, including nation-state sponsored attacks," spokesman Michael Rein said.

He said Lockheed had a three-pronged strategy to help secure its supply chain, that included education, assessment and training, as well as specific measures aimed at protecting data.

(Reporting by Andrea Shalal; Editing by Diane Craft and Cynthia Osterman)

By Andrea Shalal