The $52.6 billion U.S. intelligence arsenal is aimed mainly at unambiguous adversaries, including al-Qaida, North Korea and Iran. But top-secret budget documents reveal an equally intense focus on one purported ally: Pakistan.

No other nation draws as much scrutiny across so many categories of national security concern.

A 178-page summary of the U.S. intelligence community's "black budget" shows that the United States has ramped up its surveillance of Pakistan's nuclear arms, cites previously undisclosed concerns about biological and chemical sites there, and details efforts to assess the loyalties of counterterrorism sources recruited by the CIA.