North Korea has blasted South Korea for "having the audacity" to deploy US stealth bombers while proceeding with the June 15th joint celebration in Pyongyang.

Pyongyang radio on Monday said the deployment has poured cold water on the reconciliatory mood ahead of the event and fostered a hostile environment that may cancel the festivities.

It also accused Washington of trying to disguise a preemptive strike on the North through the deployment.

Fifteen American stealth fighters last week arrived at the Gunsan Air Base in North Jeolla Province.

The US Forces Korea said an additional 250 American airmen will undergo four months of training there.