The illegal revelation of more than 250,000 State Department documents last weekend by the WikiLeaks organization is a damaging setback for U.S. foreign policy that will strain relations with important U.S. allies, undermine U.S. national security interests, and complicate international cooperation on many issues, including the war on terrorism.

This third installment of stolen documents follows previous WikiLeaks document dumps on the wars in Afghanistan and Iraq. Like the two previous actions, this reckless release of the diplomatic cables erodes trust in the U.S. government and puts at risk American diplomats, military personnel, and intelligence professionals, as well as the foreign officials and activists that they interacted with in the course of their duties.

One of the most startling revelations to come out of the sordid WikiLeaks affair is that secret U.S. intelligence assessments concluded that Iran has obtained advanced missiles from North Korea that are much more capable than the ballistic missiles Iran was previously known to possess. According to a February 2010 diplomatic cable, Tehran received 19 BM-25 missiles from North Korea that were based on a Russian design for a submarine-launched missile. The BM-25 missiles, capable of carrying a nuclear warhead, are estimated to have a range of up to 2,000 miles, which would give Tehran the ability to strike at Moscow and other European capitals. The maximum range of Iran’s previously known ballistic missiles was thought to be 1,200 miles.

This news indicates that Iran has secretly engaged in more extensive military cooperation with North Korea’s isolated regime than was previously known. It may also mean that the extent of nuclear cooperation between the two rogue regimes has been much deeper than previously suspected.

The leaked cables are also full of expressions of concern from Arab leaders alarmed about Iran’s nuclear program. King Abdullah of Saudi Arabia urged U.S. officials to “cut off the head of the snake.” Another cable quotes the king as warning that if Iran developed nuclear weapons, “everyone in the region would do the same, including Saudi Arabia.” Bahrain’s ruler, Hamad bin Isa al-Khalifa, argued “forcefully for taking action to terminate [Iran’s] nuclear program by whatever means necessary” and maintained that “the danger of letting it go on is greater than the danger of stopping it.”

The WikiLeaks documents also contained candid and sometimes unflattering assessments of foreign leaders that are sure to ruffle feathers in many foreign capitals: British Prime Minister David Cameron was described as a political lightweight; French Prime Minister Nicolas Sarkozy was reported to be “an emperor with no clothes” who has a “thin-skinned and authoritarian personal style”; Afghan President Hamid Karzai was said to “float along on paranoia” and was dismissed as “an extremely weak man who did not listen to facts.”

The exposure of these candid cables undermines U.S. diplomatic efforts on a wide range of issues. Effective diplomacy requires building mutual trust with foreign leaders and maintaining the confidentiality of information shared about global issues, negotiations, and policy debates. The WikiLeaks revelations will put a chill on future diplomatic interactions because foreign officials will be more reluctant to speak frankly for fear of seeing their words publicized in future leaks. Such concerns will not only constrain diplomacy and information-sharing between the U.S. and other governments; it could spill over to limit information-sharing within the U.S. government.

It is extremely unfortunate that international efforts to defeat terrorism, prevent Iran from developing nuclear weapons, and build stable democracies in Iraq and Afghanistan have been compromised by the criminal disclosure of thousands of documents with no apparent purpose but to embarrass and undermine the U.S. government.