SEOUL — Officials from North Korea and the American-led United Nations Command held a “substantive” third planning session on Friday morning to prepare for higher-level talks about the March sinking of a South Korean patrol ship, a UNC spokesman said.

During the two-hour meeting at Panmunjom, officials continued to discuss protocols and the agenda for future general-officer level talks about the sinking of the patrol ship Cheonan, and agreed to hold a fourth meeting on Aug. 9, UNC spokesman David Oten said.

Officials also continued discussions about forming a joint assessment group to study the sinking, he said.

The two sides first discussed forming a joint assessment group during their last meeting on July 23. The creation of such a group could open the door for North Korean officials to come into South Korea as part of the investigation.

No other details about Friday’s colonel-level meeting were released.

A South Korean-led international investigation determined that a North Korean torpedo caused the explosion that sank the Cheonan on March 26, killing 46 crew members.

The United Nations Security Council released a statement in July condemning the sinking but did not blame North Korea. The reclusive communist country has repeatedly denied involvement.

Friday’s meeting comes two days after the end of a U.S.-South Korean exercise meant to remind North Korea of the alliance’s military strength. The U.S. announced last week that it will implement new sanctions against North Korea aimed at stopping the North’s sale and proliferation of nuclear weapons and the illegal activities that fund them.

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