South Korean authorities are scheduled to visit the U.S. for talks with Moderna representatives to resolve delays in COVID-19 vaccine shipments.

Senior Health Ministry official Son Young-rae said on Thursday that the delegation led by Second Vice Health Minister Kang Do-tae will depart at 9:30 a.m. Friday.

While the government has said the contract with Moderna doesn't specify a timetable, the delegation plans to make an official complaint and secure Moderna's promise to prevent such a recurrence.

Earlier, Moderna notified Seoul that it can only supply less than half of the eight-point-five million doses that it agreed to deliver in August, citing production issues.

This prompted authorities to extend the four-week interval between doses for Moderna vaccines and the three-week interval for Pfizer vaccines.