U.S. B-52 nuclear bombers are unlikely to participate in the ongoing Max Thunder air drills between the U.S. and South Korea.

A source in the South Korean military said on Wednesday that U.S. F-22 Raptor stealth fighters are participating in the drills, which kicked off on Friday, but B-52 bombers have not joined yet and are unlikely to take part.

A Seoul official also said that the bombers will not participate in the exercises that will continue until May 25th.

The move comes as North Korea abruptly canceled inter-Korean talks citing the massive drills. 

The B-52 is one of the pillars of the “nuclear umbrella” defense system that the U.S. provides for its key allies including South Korea. It is a long-range strategic bomber that can carry up to 31 tons of bombs. 

Meanwhile, South Korea's Defense Minister Song Young-moo and U.S. Forces Korea Commander Vincent Brooks will hold an emergency meeting on Wednesday to discuss the  North's sudden cancellation of the inter-Korean talks. 

The two sides may also discuss U.S. assets participating in the joint military drills.