The legal action comes after repeated requests filed under the US Freedom of Information Act have gone unfulfilled. They include one request AP made five years ago and others pending since the summer of 2013.
The lawsuit, filed in the US District Court for the District of Columbia, comes a day after Clinton broke her silence about her use of a private email account while secretary of state. The FOIA requests and lawsuit seek materials related to her public and private calendars, correspondence involving longtime aides likely to play key roles in her expected campaign for president, and Clinton-related emails about the Osama bin Laden raid and National Security Agency surveillance practices.
"The press is a proxy for the people, and AP will continue its pursuit of vital information that's in the public interest through this action and future open records requests," she said.
State Department spokesman Alec Gerlach declined to comment. He had previously cited the department's heavy annual load of FOIA requests 19,000 last year in saying that the department "does its best to meet its FOIA responsibilities."
Michael Oreskes, a senior managing editor at AP, said the news agency was planning to file additional requests under FOIA following the disclosure last week that Clinton used a private email account run on a server on her property outside New York while working at the State Department.
Clinton on Tuesday said she sent and received about 60,000 emails from her personal email address in her four years as President Barack Obama's secretary of state. She said roughly half were work-related, which she turned over to the State Department, while deleting tens of thousands more that were personal in nature.