WASHINGTON — The National Security Agency on Thursday disputed a published report that secret intelligence budget files provided by agency leaker Edward Snowden show that the surveillance agency warned in 2012 that it planned to investigate up to 4,000 cases of possible internal security breaches.

The Washington Post, citing documents it said were provided by Snowden, said the NSA's concerns about insider threats were aimed at "anomalous behavior" of agency employees with access to top secret data. The account cited NSA concerns about "trusted insiders who seek to exploit their authorized access to sensitive information to harm U.S. interests."

The NSA concerns were outlined in top-secret documents provided to the Senate and House intelligence committees in February 2012, well before Snowden emerged this summer as the sole source of massive new disclosures about the agency's surveillance operations. The Post released only 17 pages of the entire 178-page budget document, along with additional charts and graphs, citing conversations with Obama administration officials who voiced alarms about disclosures that could compromise intelligence sources and methods.

An NSA spokesman disputed the Post's description of the agency's planned investigation of 4,000 possible security breaches, saying the effort actually amounted to a broad investigation of personnel to lessen the possibility of security risks.

"NSA planned to initiate 4,000 reinvestigations on civilian employees to reduce the potential of an insider compromise of sensitive information and missions," agency spokesman Vanee M. Vines said late Thursday. "Periodic reinvestigations are conducted as one due-diligence component of our multifaceted insider threat program."

Vines said such reinvestigations are required under a 2008 federal directive governing high-security clearances for intelligence workers.

As of Thursday night, the Post had not amended its reporting.

It was not clear from the Post's reporting how many of the 4,000 cases ultimately were investigated or how many posed serious breaches of security. Steven Aftergood, head of a project on government secrecy at the Federation of American Scientists in Washington, questioned whether many of the reported 4,000 cases were credible.

Referring to previous reports that the NSA's classified work force totals nearly 40,000, Aftergood said, "It would be hard to believe that one in every 10 NSA employees is a possible threat." He suggested that many cases might be caused by internal warnings arising from minor internal protocol errors or mistakenly accessed documents.

But aggressive high-profile Justice Department prosecutions in recent years of several former NSA staffers have shown the agency taking a toughened stance in cracking down on possible leaks. "In any case, a number that large is striking," Aftergood said.

The latest revelations also disclosed limited details about the highly classified 2013 intelligence "black budget," which previously only provided a topline of nearly $53 billion. The $52.6 billion intelligence budget described by the Post discloses that the NSA's portion was $10.5 billion in 2013 – outstripped only by the CIA's $14.7 billion.

Aftergood said the CIA's budget growth from $3 billion in the 1990s to nearly $15 billion likely reflects its post-9/11 push into drone warfare and paramilitary operations overseas.

The Post's story also said the NSA and CIA were engaged deeply in offensive cyber operations and had conducted counterintelligence operations against the governments of Israel and Pakistan as well as traditional targets such as Iran, Russia, China and Cuba. The Post also reported that the NSA considers North Korea the hardest intelligence target to crack and said U.S. officials know almost nothing about the plans of North Korean leader Kim Jong Un.