Hundreds of thousands of State Department documents leaked Sunday revealed a hidden world of backstage international diplomacy, divulging candid comments from world leaders and detailing occasional U.S. pressure tactics aimed at hot spots in Afghanistan, Iran and North Korea.

The classified diplomatic cables released by online whistle-blower WikiLeaks and reported on by news organizations in the United States and Europe provided often unflattering assessments of foreign leaders, ranging from U.S. allies such as Germany and Italy to other nations like Libya, Iran and Afghanistan.

The cables also contained new revelations about long-simmering nuclear trouble spots, detailing U.S., Israeli and Arab world fears of Iran's growing nuclear program, American concerns about Pakistan's atomic arsenal and U.S. discussions about a united Korean peninsula as a long-term solution to North Korean aggression.

There are also American memos encouraging U.S. diplomats at the United Nations to collect detailed data about the U.N. secretary general, his team and foreign diplomats — going beyond what is considered the normal run of information-gathering expected in diplomatic circles.

None of the revelations is particularly explosive, but their publication could prove problematic for the officials concerned. And the massive release of material intended for diplomatic eyes only is sure to ruffle feathers in foreign capitals, a certainty that prompted U.S. diplomats to scramble in recent days to shore up relations with key allies in advance of the disclosures.