Panamanian authorities detained a North Korean-flagged ship and its crew as they headed for North Korea from Cuba carrying what U.S. officials suspect are components of a surface-to-air missile system.
U.S. officials said the intercepted cargo is of potential worry if it indicates a growing bilateral arms trade between North Korea and Cuba.
Analysts said Cuba's role in the arms shipment could derail efforts to improve relations with the U.S.
Panamanian President Ricardo Martinelli on Monday night said intelligence information had indicated the North Korean-flagged Chong Chon Gang might be carrying drugs, but that "containers with sophisticated missiles" were found under containers of sugar.
U.S. officials later said that according to preliminary information, there were no missiles aboard the ship.
Late Tuesday, Cuba's foreign ministry said the vessel, which was carrying 10,000 tons of sugar, was also loaded with 240 metric tons of "obsolete defensive weapons" built in the mid-20th century. These included nine disassembled missiles, two MiG-21 Bis jet fighters, and two disassembled antiaircraft missile complexes, "to be repaired and returned to Cuba."
Cuba said the shipment of these weapons to North Korea is "supported by the need to maintain our defensive capacity in order to preserve national sovereignty." It wasn't clear if Cuba's acknowledgment of its ownership of the weapons would be enough to quell the controversy.
Panama's security minister, José Raul Mulino, told Radio Panama on Tuesday that workers were safely unloading the sensitive cargo onto docks. He said the case would likely be referred to the United Nations, which strictly prohibits unauthorized, undeclared shipments of weapons of this type.
"They must be missiles, missile launchers, etc., something like that.…I'm no weapons expert," Mr. Mulino said after taking a look at the cargo.
U.S. officials said they believe the North Korean ship picked up a key radar component from Cuba of an SA-2 surface-to-air defense system, which many countries still use.
It was an SA-2 that shot down the American U-2 spy plane piloted by U.S. aviator Francis Gary Powers in 1960, according to an Air Force website.
The North Korean ship was transporting what U.S. officials believe was the fire-control radar system from an SA-2 used for targeting, U.S. officials said.
It remained unclear why North Korea might be importing weapons from communist Cuba, one of its few global allies. The isolated Asian state has had a weapons-export business for many years, shipping missile technology and weapons to countries such as Syria and Myanmar.
Some defense experts said they believe the ship may have been transporting the radar to North Korea for an upgrade, a sign the Cubans may be paying Pyongyang for improved weapons technology.
The U.S. and Panama had been tracking the ship for several days, suspecting it was carrying weapons and that it was going to try to transit the canal, said a U.S. official.
U.S. officials said they hoped Panama would stop the ship to inspect it, and publicly praised Panama for doing so. "The U.S. was aware of the suspected shipment and believed the Panamanian officials were going to stop it," a U.S. official said.
A State Department spokesman, Patrick Ventrell, said the U.S. has pushed for enforcement of U.N. resolutions restricting North Korean weapons activities. "Any shipment of arms would violate numerous U.N. security resolutions," he said.
Kim Kyok Sik, the head of North Korea's armed forces, visited the island two weeks ago, meeting with President Raúl Castro, Cuba's official media reported.
North Korea was taken off the U.S. State Sponsor of Terrorism list in 2008 after it agreed to inspection of its nuclear program. Cuba remains on the list.
In Washington, Cuban-born Rep. Ileana Ros-Lehtinen, (R., Fla.) called for the U.S. to return North Korea to the terror list, and to cancel migration talks between the U.S. and Cuba until Havana "provides clear and coherent answers regarding this incident."
North Korea, which staged a nuclear-weapons test in February, is expected to hold a large military rally this month to mark the July 27 anniversary of the armistice in the Korean War.
In 2009, authorities in Bangkok discovered 40 tons of rocket launchers and other weapons that U.S. and other investigators said was part of a North Korean arms smuggling network.
The weapons apparently were coming from North Korea, making a refueling stop in Thailand before heading to an unknown destination.
London-based defense and intelligence research firm IHS, based on images released, identified a piece of equipment as a "Fan Song," or fire-control radar, for surface-to-air missiles of the SA-2 family.
"It could be equipment going to North Korea to be upgraded," said Neil Ashdown, IHS's Asia-Pacific analyst.
Mr. Ashdown said if the equipment were going to North Korea for upgrading, it would be returned to Cuba, or it could be going there to stay.
North Korea operates a lot of similar type of equipment, he added. "These would be for a high-altitude air-defense system."
The detection of the shipment could be a setback for relations between Cuba and the U.S. that seemed to be on the mend, analysts said.
"This certainly won't help our relationship with Cuba," said Jay Cope, a senior research fellow at the Institute for National Strategic Studies, which is affiliated with the U.S. Defense Department. "Cuba says it doesn't do anything on terrorism. This raises the question of whether we can believe them."
Added Riordan Roett, the head of Latin American studies at Johns Hopkins University: "This is going to give plenty of support to lawmakers that are consistently saying that relations with Cuba should not be liberalized and that Cuba can't be trusted."
Mr. Mulino, Panama's security minister, said Panamanian officials began tracking the ship on July 10, and when it approached the Panama Canal on Friday, they used the narrow waterway to corner and capture it.
He said members of the Panamanian navy who boarded and inspected the ship had to deal with a captain who tried to commit suicide at the time ship was detained, and a crew that tried to riot and keep the hidden cargo from being discovered.
Once the captain and crew were secured and taken off the ship, authorities guided it to a port on the Atlantic coast. Using X-ray scanners, they found the illegal load under thousands of small bags of brown sugar, Mr. Mulino said.
"So that the world knows: You can't be passing undeclared bellicose materiel through the Panama Canal. The Panama Canal is a canal of peace, not a canal of war," said Mr. Martinelli.
For years, the U.S. has repeatedly insisted that North Korea make good on previous commitments to unwind its nuclear program.
But North Korea, known formally as the Democratic People's Republic of Korea, says it will never unilaterally give up its "treasured sword" of nuclear weapons.
Hugh Griffiths, an expert on arms trafficking from the Stockholm International Peace Research Institute, said the risks for North Korea in the smuggling operation were low.
"There is no reputational risk. North Korea is an international pariah," he said, adding that he believes the crew, and perhaps even the sugar, will still be allowed to continue on back to North Korea.
Millions in North Korea face the prospect of food shortages this year. The U.N.'s Food and Agriculture Organization said supply is expected to fall short this year despite a relatively stable grain harvest last year.
—José de Córdoba,
and Darcy Crowe
contributed to this article.