Iran bought 19 advanced missiles from North Korea, a diplomatic cable says. The North displayed what some experts say are the same kind of missiles in an October parade.

Secret American intelligence assessments have concluded that Iranhas obtained a cache of advanced missiles, based on a Russian design, that are much more powerful than anything Washington has publicly conceded that Tehran has in its arsenal, diplomatic cables show.

Iran obtained 19 of the missiles fromNorth Korea, according to a cable dated Feb. 24 of this year. The cable is a detailed, highly classified account of a meeting between top Russian officials and an American delegation led by Vann H. Van Diepen, an official with the State Department’s nonproliferation division who, as a national intelligence officer several years ago, played a crucial role in the 2007 assessment of Iran’s nuclear capacity.

The missiles could for the first time give Iran the capacity to strike at capitals in Western Europe or easily reach Moscow, and American officials warned that their advanced propulsion could speed Iran’s development of intercontinental ballistic missiles.

There has been scattered but persistent speculation on the topic since 2006, when fragmentary reports surfaced that North Korea might have sold Iran missiles based on a Russian design called the R-27, once used aboard Soviet submarines to carry nuclear warheads. In the unclassified world, many arms control experts concluded that isolated components made their way to Iran, but there has been little support for the idea that complete missiles, with their huge thrusters, had been secretly shipped.

The Feb. 24 cable, which is among those obtained by WikiLeaks and made available to a number of news organizations, makes it clear that American intelligence agencies believe that the complete shipment indeed took place, and that Iran is taking pains to master the technology in an attempt to build a new generation of missiles. The missile intelligence also suggests far deeper military — and perhaps nuclear — cooperation between North Korea and Iran than was previously known. At the request of the Obama administration, The New York Times has agreed not to publish the text of the cable.

The North Korean version of the advanced missile, known as the BM-25, could carry a nuclear warhead. Many experts say that Iran remains some distance from obtaining a nuclear warhead, especially one small enough to fit atop a missile, though they believe that it has worked hard to do so.

Still, the BM-25 would be a significant step up for Iran.