What South Korea's new president means for North Korea

SEOUL, South Korea -- The inauguration of Yoon Suk-yeol as the 20th president of South Korea took place at the National Assembly compound in Seoul on Tuesday, marking the start of his five-year term.

Facing an economy hit hard by the pandemic, surging home prices and a politically polarized country, Yoon's biggest and imminent challenge is the constant threat of North Korea, which has sped up its nuclear weapons program while test-firing missiles 15 times just this year alone.

"The door to dialogue will remain open so that we can peacefully resolve this threat," President Yoon said during his inauguration speech. Under the condition that North Korea "genuinely embarks on a process to complete denuclearization," the new South Korean government will present "an audacious plan" to help Pyongyang strengthen its hardstricken economy and "improve the quality of life for its people," Yoon added.

But prospects are grim for a peaceful resolution between the two Koreas. Yoon, characterized as a "man of principle" and "predictability," has repeatedly warned that North Korea's bad behavior will not be rewarded.

Analysts also doubt that Pyongyang will change its path, especially after its leader Kim Jong Un declared last month that "the nuclear forces, the symbol of our national strength and the core of our military power, should be strengthened in terms of both quality and scale."

Analysts say more variety of weapons tests, especially tactical nuclear weapons and submarine-launched missile systems, are very likely to follow with the aim to minimize nuclear warheads.

"For tactical nuclear weapons to be deployed, they have to test a tactical nuclear warhead. So it's not going to be a bigger sized scale of the nuclear test, but they probably need to have a nuclear warhead test very soon to show that they have that capability," Dr. Woo Jung-yeop of the Seoul-based Sejong Institute told ABC News.

Yoon, married to first lady Kim Gun-hee with no children, spent 27 years of his entire career as a prosecutor with no political experience. He rose to prominence for standing up against political and social pressure when convicting numerous big political players, including two former presidents, Park Geun-Hye and Lee Myung-bak. He was appointed as Prosecutor General in 2019 by then-President Moon Jae-in for that reason, but was ironically pushed out by Moon's Democratic Party politicians last year for his principled manners against their radical reformist policies. Yoon had run for office as the opposition conservative People Power Party's presidential candidate.

ABC News' Hakyung Kate Lee contributed to this report.