North Korean officials were due in Panama Wednesday to secure the release of 35 sailors being held for allegedly smuggling undeclared weapons from Cuba in an apparent violation of UN sanctions.

Political counselor Ra Yun Bak and Havana-based diplomat Ri Il Gyu were to visit for two days to discuss the sailors' fate with prosecutor Javier Caraballo, a government source said.

The sailors were on board the Chong Chon Gang, which was intercepted July 10 as it tried to enter the Panama Canal on suspicion it was carrying drugs.

Authorities instead uncovered 25 containers of military hardware, including two Soviet era MiG-21 fighter jets, air defense systems, missiles and command and control vehicles.

Both Havana and Pyongyang said they were "obsolete" Cuban arms being shipped to North Korea for refurbishment under a legitimate contract.

The communist allies did not explain why the items were buried under more than 200,000 sacks of sugar.

The ship's 35 crew members are being detained at a former US military base on arms trafficking charges. They face up to 12 years in prison if convicted.

The Panama Canal Authority announced in September that it had slapped a $1 million fine on the ship.

In August, the Panamanian government said the United Nations had determined that the shipment violated sanctions against arms transfers to North Korea.

The sanctions were imposed over the reclusive country's controversial nuclear program.