South Korea stepped up the scale of joint militaryexercises with US as it announced on Thursday that it had staged joint air drills with the United States, featuring strategic bombers and stealth fighters.

The drills on Wednesday showed "the US's will and capabilities to provide strong and credible extended deterrence against North Korea's nuclear and missile threats," the South Korean Defence Ministry said.

The exercises came a day after US Defense Secretary Lloyd Austin and his South Korean counterpart vowed to boost security cooperation to counter an increasingly belligerent nuclear-armed North Korea.

The exercises involved American B-1B long-range heavy bombers and stealth fighters -- US Air Force F-22s and South Korean F-35s -- flying over the Yellow Sea, the ministry added.

North Korea has lambasted South Korea and the United States over their joint military exercises, saying the drills have pushed the situation on the Korean peninsula to an "extreme red line" and have threatened to turn the region into a "huge war arsenal and a more critical war zone".

The North Korean statement, issued on Thursday, also threatened the "toughest" response and said Pyongyang was not interested in dialogue as long as Washington pursued what it called "hostile" policies.

Austin and South Korean Defence Minister Lee Jong-sup agreed this week to "expand and bolster the level and scale" of joint military exercises in light of "continued provocations" from Pyongyang, including a recent drone incursion into the South.

The two also said they would expand cooperation that includes Japan to better share information and coordinate responses to provocations from Pyongyang, which fired off a record number of ballistic missiles last year. North Korea for decades has denounced the joint drills as a prelude to an invasion and war.

“Our commitment to the defense of the ROK remains ironclad,” Austin said, referring to South Korea by its formal name. “The United States stands firm in its extended deterrence commitment and that includes the full range of US defense capabilities including our conventional, nuclear and missile defense capabilities.”

Bolstering US-South Korean military drills and deploying strategic weapons to the region was akin to "talking about the use of nuclear weapons against the DPRK", the North Korean statement on KCNA said, using the country's official name.

It warned that North Korea would follow the "principle of 'nuke for nuke' and an all-out confrontation for an all-out confrontation!'"

"The DPRK is not interested in any contact or dialogue with the U.S. as long as it pursues its hostile policy and confrontational line," it added.

Image source: NDTV