US President Donald Trump’s pick of defense hawk John Bolton as his new security adviser is fueling concerns in South Korea that Washington is shifting to a tougher stance on North Korea ahead of its planned summit with Pyongyang.

Trump announced in a tweet he had tapped as his new national security adviser Bolton, a Fox News analyst and former US ambassador to the United Nations known for his hard-line stance advocating the use of military force against North Korea and Iran.

The decision to replace H.R. McMaster with Bolton is a strong signal that Washington will not tolerate Pyongyang prolonging negotiations without its commitment to denuclearization, and the situation could take a dramatic hawkish turn if talks fail to yield results, experts here say.

“The appointment of Bolton is very worrisome for South Korea,” said Park Won-gon, a professor at Handong Global University, describing Bolton as “unimaginably hawkish.” “It raises the possibility of the US taking military action, or seeking a regime change in the North if the talks fail.”

Bolton is a neoconservative who thinks democracy should be promoted even when that requires using a military option, and he seems to believe that North Korea will not give up its nuclear weapons programs through dialogue, Park added.

“But appointing him may not just be a bad thing. The personnel shake-up made it clear what measures the US will take when talks fail -- such as a military option or regime change. And the North also knows that.”

The US and North Korea are preparing to hold talks by the end of May over the North’s nuclear and missile programs, in a surprising breakthrough following a year of hostilities and insults between the leaders. The two Koreas are also scheduled to hold a summit in late April.

Bolton, who served in the Republican administrations of Ronald Reagan, George H.W. Bush and George W. Bush, has struck a hawkish tone on North Korea.

In 2003, when he was an undersecretary in the State Department under President George W. Bush, Bolton denounced then-North Korea’s leader Kim Jong-il as a “tyrannical dictator,” “human scum and bloodsucker.” He also said North Korea is where “life is a hellish nightmare.”

His views do not appear to have changed despite the US’ recent diplomatic opening with North Korea.

“It is perfectly legitimate for the United States to respond to the current ‘necessity’ posed by North Korea’s nuclear weapons by striking first,” Bolton said last month in a Wall Street Journal column titled ”The Legal Case for Striking North Korea First.”

In September last year, Bolton said on Fox News, “I think the only diplomatic option left is to end the regime in North Korea by effectively having the South take it over.”

But Bolton, who is scheduled to start his new job on April 9, seems to be distancing himself from his previous hawkish comments, saying “What I have said in private now is behind me.”

“The important thing is what the president says and the advice I give him,” he said on Fox News’ “The Story” aired Thursday after he was tapped as Trump’s new security adviser.

Shin Beom-chul, professor at the Korea National Diplomatic Academy, said that the US-North Korea summit will likely be held as planned, but there is now a higher possibility of talks ending in failure.

“The Trump administration will more strongly push for complete, verifiable and irreversible denuclearization of North Korea now. If North Korea is sincere about denuclearization, it won’t be a problem,” Shin said. 

“But if North Korea wants to make a compromise over its nuclear programs, there is a lower possibility of any agreement between the two countries being made."

The move comes as part of Trump’s continued reshuffle of personnel in the White House, filling his foreign policy team with hard-liners.

Trump fired Secretary of State Rex Tillerson, one of the advocates for diplomacy with North Korea, replacing him with Mike Pompeo, former director of the Central Intelligence Agency. Pompeo is also seen as a hard-liner who has floated the possibility of a pre-emptive strike against North Korea and its regime change. 

A Cheong Wa Dae official said Seoul would continue communicating closely with Washington.

“Our stance is that if a new road opens, we have to go that path,” a senior Blue House official told reporters on condition of anonymity. “Bolton has knowledge on issues regarding the Korean Peninsula and most of all, we know him to be one of the US president’s aides who is trusted.”

South Korean President Moon Jae-in has strived to use the momentum created by North Korea’s participation in the PyeongChang Olympics to lead North Korea and the US into dialogue to resolve North Korea’s nuclear issue.

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)