South Korea and the United States will begin their annual joint military exercises next week with a focus on improving combined capabilities to deter and defend against growing North Korean nuclear threats, the allies said.

The drills could trigger a belligerent response from North Korea, which portrays them as invasion rehearsals and has used the allies’ military co-operation as a pretext to advance the development of nuclear weapons and missile systems.

South Korean and US military officials said this year’s Ulchi Freedom Shield exercise, scheduled for August 19 to 29, will include computer-simulated exercises designed to enhance readiness against such threats as missiles, GPS jamming and cyber attacks, as well as concurrent field manoeuvres and live-fire exercises.

The allies in particular aim to “further strengthen (their) capability and posture to deter and defend against weapons of mass destruction”, military officials said in a joint news conference.

Lee Sung Joon, spokesperson of South Korea’s Joint Chiefs of Staff, said about 19,000 South Korean troops will participate in the drills, which he described as an “essential element for maintaining a strong defence posture to protect the Republic of Korea”, using South Korea’s formal name.

Ryan Donald, spokesperson of US Forces Korea, did not comment on the number of US troops participating in the exercises and said he could not immediately confirm whether the drills will involve US strategic assets.

The United States has in recent months increased its regional deployment of long-range bombers, submarines and aircraft carrier strike groups to train with South Korean and Japanese assets in a show of force against the North.

“This exercise will reflect realistic threats across all domains such as the Democratic People’s Republic of Korea’s missile threats and we will take in lessons learned from recent armed conflicts,” Mr Donald said, invoking the North’s formal name.

“ROK and US units will execute combined field training exercises across all domains. Field manoeuvre and live fire exercises will strengthen the alliance’s interoperability while showcasing our combined capabilities and resolve,” he said.

In addition to its military exercises with the United States, the South Korean military will support the country’s civil defence and evacuation drills on August 19-22, which will include programmes based on North Korean nuclear attack scenarios, Mr Lee said.

Animosity on the Korean Peninsula is high as North Korean leader Kim Jong Un continues to use Russia’s war on Ukraine as a window to accelerate weapons development while issuing verbal threats of nuclear conflict towards Washington and Seoul.

In response, South Korea, the United States and Japan have been expanding their combined military exercises and sharpening their nuclear deterrence strategies built around US strategic assets.

During last year’s Ulchi Freedom Shield exercises, North Korea conducted ballistic missile tests that it described as simulating “scorched earth” nuclear strikes on South Korean targets.

South Korea’s military said on Monday that the North launched about 240 balloons, but only 10 were known to have landed in the South, all in areas north of the capital Seoul.

Those balloons carried paper waste and plastic bottles, and no dangerous substances were found, the South’s joint chiefs said.

It was the first time North Korea flew balloons towards the South since July 24, when rubbish carried by at least one of them fell on the South Korean presidential compound, raising worries about the vulnerability of key South Korean facilities.

The balloon contained no dangerous material and no-one was hurt.

Also on Monday, South Korean President Yoon Suk Yeol nominated presidential security chief Kim Yong-hyun, one of his closest confidants, as defence minister.

Mr Kim will be replacing Shin Won-sik, who was picked to be Mr Yoon’s new national security adviser, according to the presidential office.

As a nominee for a cabinet job, Mr Kim is subject to a parliamentary hearing, although Mr Yoon can appoint him even if legislators object.

Mr Yoon, a conservative, has struggled to push his agenda through the opposition-controlled National Assembly.

The liberals have often criticised Mr Yoon’s national security policies as hawkish and called for stronger efforts to revive dialogue with the North.