Cuba admitted that the ship that was stopped last week as it headed into the Panama Canal carried what it described as obsolete weapons systems that were due to be repaired in North Korea.

Panamanian authorities held the vessel after they were tipped off there might be drugs on board. Instead, they found what looked like missiles hidden under a cargo of sugar, Panama’s president Ricardo Martinelli said on Tuesday. “That is not allowed. The Panama canal is a canal of peace, not war,” he told a local radio station.

North Korea is prohibited under international sanctions from importing weapons that it might use to advance its nuclear program. “Shipments of arms or related materiel to and from Korea would violate Security Council resolutions, three of them as a matter of fact,” said the United States’ ambassador to the United Nations, Rosemary DiCarlo, who chairs the Security Council this month.

Cuba’s claim that the weapons were due to be repaired in North Korea and then send back might circumvent the embargo although it seems doubtful Panama will allow the shipment to go through.

The island nation, which is ideologically aligned with communist Korea, said the cargo included anti-aircraft batteries, two fighter jets and fifteen fighter jet engines as well as nine disassembled rockets — all Soviet era weaponry built in the middle of the twentieth century. North Korea’s armed forces are equipped with material from the same period.

In a statement that was read out on state television, Cuba argued that the weapons were required to “maintain our defensive capacity.” It added, “Cuba maintains its commitment to peace including nuclear disarmament and international law.”

An American official cited by the Reuters news agency speculated that Cuba sent the missile parts to North Korea for an upgrade with the sugar to pay for the work. Sugar cane is one of Cuba’s primary export products.

The two communist states were driven into a closer relationship following the collapse of the Soviet Union in 1991 which denied them both considerable economic aid and diplomatic cover. American sanctions might only strengthen what would otherwise seems an alliance of necessity. Whereas Cuba reacted to the Soviet Union’s demise by letting in tourists, North Korea remained isolated. Its economy lost more than half of its value and a million people are believed to have died in famines between 1994 and 1998. Cuba is cautiously experimenting with market reforms and altogether a far less oppressive place. Liberalization in North Korea still seems far off.