TOKYO (BLOOMBERG) - Japan and South Korea look set to try to revive a relationship that has hit new depths in recent years, with President-elect Yoon Suk-yeol offering an olive branch to Tokyo weeks before US President Joe Biden is likely to visit both countries.

Mr Yoon, who takes office on May 10, is sending a group of South Korean lawmakers and policy experts to Japan for a five-day stay from Sunday (April 24), after saying he is looking to reset troubled ties.

He has already sent a delegation to the United States and will next send envoys to China before his inauguration.

Warming ties between the two US allies would be a welcome development for the Biden administration as it seeks cooperation from Seoul and Tokyo to counter security threats posed by China and North Korea, while securing supply chains for key goods such as semiconductors free from interference from Beijing.

Mr Yoon, a conservative, has signalled he wants to take a hawkish diplomatic course, which would also be in line with some of the security priorities of the conservative government of Japanese Prime Minister Fumio Kishida.

The new leadership in Seoul may offer a chance to inch back relations to something more like normal, with the war in Ukraine providing a reminder to both countries of their reliance on their mutual ally amid growing regional threats.

"Under the Yoon administration, we can see a way forward to restoring ties," said Professor Yasuyo Sakata of Kanda University of Foreign Studies in Chiba, Japan, who specialises in East Asian security, adding that there will be chances to show that the neighbours "are more on the same wavelength".

The delegation's visit to Japan is set for a month before Mr Biden - a staunch advocate of alliances - is expected to arrive in the region and visit both South Korea and Japan.

It also comes weeks after North Korea fired off a missile for the first time since 2017 with a range that could hit the US mainland and as it looks set to conduct its first nuclear test in nearly five years.

Ties between Tokyo and Seoul plunged to their worst state in decades under outgoing president Moon Jae-in - a progressive - and former Japanese prime minister Shinzo Abe - a conservative - over whether Tokyo had shown proper contrition and sufficiently compensated for its 1910 to 1945 colonisation of the Korean peninsula.

That led to strains in security cooperation and frequent bickering between the two countries that host the bulk of US troops in the region.

"Yoon realises the US is needed for South Korea's security, and therefore the need to mend ties with another major US ally in the region: Japan," said political science professor Shin Yul at Myongji University in Seoul.

"The question is whether to prioritise history or security, and Yoon is likely to prioritise the latter, given his vows during the election campaign and his actions after the victory."

But there are limits to how close Mr Yoon can get after his two conservative predecessors as president faced backlash at home for being seen as being too accommodating to Japan, which caused sharp falls in support and hampered their policy agendas.

Mr Yoon cannot afford any missteps as he enters office with some of the lowest approval levels for a new South Korean president and faces a Parliament where his progressive opponents hold a supermajority.

Japan would like to see a halt to compensation cases brought over Korean workers conscripted to work in Japanese factories and mines during the colonial period, but any attempts by Mr Yoon to intervene could be seen as threatening the judiciary's independence and further undermine support for his government.

Mr Yoon's camp has indicated it may seek a two-track approach with Japan, trying to improve cooperation on security, while pressing Tokyo to show what Seoul sees as greater accountability for widespread harm to millions of Koreans before and during World War II.

Mr Kishida was one of the first world leaders to congratulate Mr Yoon on his victory and has repeatedly said since then that good ties with Seoul are "indispensable in realising a rules-based international order and ensuring peace".

Yet it remains unclear whether Mr Kishida will meet the South Korean delegation this week, or what level of envoy he will send to Mr Yoon's inauguration - another event that could help set the tone for ties with his new counterpart.

Kyodo News reported on Friday that Mr Kishida is likely to meet the delegation and may discuss the possibility of attending the inauguration.

"Moon's position was the Japanese government's worst nightmare," said Dr Lauren Richardson, director of the Australian National University's Japan Institute.

"The Japanese side are being very cautious until they have some concrete indication that Yoon's position will represent a departure."