Moderna agreed to expand its supply of COVID-19 vaccines to South Korea in August and September and to advance the supply schedule for September.

This comes after a South Korean delegation led by Second Vice Health Minister Kang Do-tae recently visited the U.S. to lodge a complaint with the company, after it cut its August supply by more than half, citing production problems.

At a press briefing on Tuesday, Kang said he called for the early delivery of vaccines scheduled for the third quarter and a stable overall supply for Moderna to regain public trust and continue cooperation with Seoul.

Apologizing for the sudden shortage that caused disruptions to South Korea's vaccination program, Moderna said its July shipments are gradually picking up speed after the production problem was resolved.

The delegation requested the U.S. company to deliver the delayed vaccines by early September at the latest, advance deliveries and swiftly notify Seoul of a detailed schedule. Moderna has agreed to notify Seoul by the end of this week.