The US Navy intercepted a North Korean ship suspected of carrying missiles or other weapons to Myanmar and made it turn back, a senior US official said Monday.
The comments by Gary Samore, special assistant to President Barack Obama on weapons of mass destruction, confirmed reports of the incident, which happened last month, in The New York Times and South Korean media.
The New York Times said the ship was intercepted south of the Chinese city of Shanghai by a US destroyer on May 26.
In an interview with Yonhap news agency, Samore identified the cargo ship as the M/V Light and said it may have been bound for Myanmar with military-related contraband, such as small arms or missile-related items.
"We talked directly to the North Koreans. We talked directly to all the Southeast Asian countries including Myanmar, urging them to inspect the ship if it called into their port," he was quoted as saying.
"The US Navy also contacted the North Korean ship as it was sailing, to ask them where they were going and what cargo they were carrying."
North Korea is subject to international and United Nations sanctions designed to curb its missile and nuclear programmes.
UN Resolution 1874, adopted in June 2009, one month after the North's second nuclear test, toughened a weapons embargo and authorised member states to intercept such shipments.
Another North Korean ship, the Kang Nam I, was forced to reverse course in 2009 after being suspected of trying to deliver military-related supplies to Myanmar.
The New York Times said the Light was registered in Belize, whose authorities gave the United States permission to inspect the ship.
It said the US destroyer McCampbell caught up with the Light somewhere south of Shanghai and asked to board the vessel under the authority given by Belize.
The paper, quoting unidentified US officials, said the North Korean refused four times. But a few days later, it stopped dead in the water and turned back to its home port, tracked by US surveillance planes and satellites.
"Such pressure from the international community drove North Korea to withdraw the ship," Samore was quoted by Yonhap as saying.
"This is a good example that shows that international cooperation and coordination can block the North's weapon exports."
The United States has frequently expressed concern at military ties between Myanmar and North Korea.
Last month Deputy US Assistant Secretary for East Asia and Pacific Affairs Joseph Yun expressed concern directly to Myanmar's new army-backed government.
US diplomatic memos released last year by the website WikiLeaks said Washington has suspected for years that Myanmar ran a secret nuclear programme supported by Pyongyang.
A top Myanmar official told visiting US Senator John McCain this month that his country is not wealthy enough to acquire nuclear weapons.