WASHINGTON  President Obama declared on Tuesday that “no information may remain classified indefinitely” as part of a sweeping overhaul of the executive branch’s system for protecting classified national security information.

In an executive order and an accompanying presidential memorandum to agency heads, Mr. Obama signaled that the government should try harder to make information public if possible, including by requiring agencies to regularly review what kinds of information they classify and to eliminate any obsolete secrecy requirements.

“Agency heads shall complete on a periodic basis a comprehensive review of the agency’s classification guidance, particularly classification guides, to ensure the guidance reflects current circumstances and to identify classified information that no longer requires protection and can be declassified,” Mr. Obama wrote in the order, released while he was vacationing in Hawaii.

He also established a new National Declassification Center at the National Archives to speed the process of declassifying historical documents by centralizing their review, rather than sending them in sequence to different agencies. He set a four-year deadline for processing a 400-million-page backlog of such records that includes archives related to military operations during World War II and the Korean and Vietnam Wars.