WASHINGTON (Reuters) - Prosecutors running a U.S. leak probe told the Associated Press about a seizure of the news agency's phone records within 90 days of taking them as it was required to do, a Justice Department official said on Tuesday.

Peter Kadzik, a deputy assistant attorney general, wrote in a letter to lawmakers that the search was not secret, that the search of 2012 records was conducted in 2013, and that the department complied with its notification obligation.

The AP has reported that prosecutors notified the news agency on May 10, 2013, that the government seized records from April and May 2012 for more than 20 separate phone lines assigned to AP and its journalists.

The Justice Department had not previously said when the seizure took place. Kadzik's letter sought to clarify that it happened this year and argues the seizure was not "secret," as AP has described it in news reports.

Notification to a media outlet must take place within 90 days, and "that requirement was met in this matter," he wrote.

Kadzik offered no explanation for why the Justice Department did not seek to negotiate access with the AP, as would normally occur before seizing media records with a subpoena.

"There are a number of reasons - depending on the circumstances of a given case - that may lead the department to refrain from negotiating with a media organization," he wrote.

A spokeswoman for the AP did not immediately respond to a request for comment on the letter.

The leak probe is focused on how AP reporters learned about a U.S. operation in Yemen to foil a plot to bomb an airliner, government officials have said.

An AP story in May 2012 described the plot. The AP has reported that it delayed publishing the story at the request of government officials until security concerns were allayed.

U.S. officials have said, however, that the leak compromised a U.S. agent working to undermine Yemen-based Al Qaeda in the Arabian Peninsula.

AP CEO Gary Pruitt said in a statement last month that Justice Department explanations had been inadequate.

"Rather than talk to us in advance, they seized these phone records in secret, saying that notifying us would compromise their investigation. They offer no explanation of this, however," Pruitt said.

Journalists, lawmakers and civil liberties advocates have said recent disclosures about Justice Department tactics involving reporters raised concern about the U.S. commitment to press freedom.

At President Barack Obama's direction, Attorney General Eric Holder is reviewing Justice Department's guidelines for investigations that involve reporters, although Holder has said that prosecutors followed all laws and guidelines in recent cases.

(Reporting by David Ingram; Editing by Howard Goller, Eric Beech and Cynthia Osterman)