SEOUL, Jul. 11 (Reuters): South Korea, Japan and the United States conducted a joint air drill on Friday involving a U.S. B-52 strategic bomber and fighter jets of the two U.S. allies over international waters, the South's defence ministry said.

It was the first time this year that a U.S. B-52H strategic bomber was deployed to the Korean Peninsula for a drill, conducted to improve deterrence against North Korea's increasing nuclear and missile threats, it said.

The three countries' defence chiefs also held an annual meeting in Seoul on Friday, where they recognised the importance of close trilateral cooperation in addressing security challenges posed by North Korea, in the Indo-Pacific and beyond, the defence ministry said in a statement.

"We're illuminating a future path together, a path where partnerships can evolve through persistent and regular engagement from building capacity to really sharing responsibility," U.S. Chairman of the Joint Chiefs of Staff General Dan Caine said in opening remarks before the meeting.

"(North Korea) and China are undergoing an unprecedented military build up with a clear and unambiguous intent to move forward with their own agendas. We need to be mindful of that," Caine said.