South Korea, China and Japan hold their first leadership summit in more than three years Sunday, marking a victory for political, and particularly economic pragmatism over historical antipathy and territorial rivalry.

The triumph of realpolitik will be capped by a first ever one-on-one summit between South Korean President Park Geun-Hye and Japanese Prime Minister Shinzo after an extended diplomatic freeze.

The trilateral gathering resumes what was originally an annual process until tensions between Northeast Asia's three largest economies in 2012 triggered a lengthy hiatus.

"China hopes the meeting will be an opportunity for the three countries to review the past and find a way out of their difficulties," Chinese Foreign Ministry spokesperson Hua Chunying said last week.

The focus will be very much on economic cooperation, with China especially keen to boost trade links as it seeks to inject some fresh momentum into its slowing economy.

Also high on the agenda will be how to deal with North Korea whose nuclear weapons ambitions pose a worry -- and threat -- to all three countries, including China, which is the North's main diplomatic protector and economic benefactor.

- Regional tensions -

Lurking in the background will be growing military tensions in the South China Sea between China and the United States, which is the chief military ally of both South Korea and Japan.

The trilateral meet will actually fall slightly below the full summit level, with China represented by Premier Li Keqiang, rather than President Xi Jinping.

Observers say Li's comparatively technocratic style should make it easier to keep the focus on economic cooperation and away from the sensitive issues that have dogged relations for decades.

Relations between Seoul and Tokyo have never been easy -- clouded by sensitive historical disputes related to Japan's 1910-45 colonial rule over the Korean peninsula, especially the issue of Korean women forcibly recruited to work in Japanese wartime military brothels.

Park, who took office in early 2013, had until now repeatedly refused to meet Abe, saying Japan had yet to properly atone for its past actions.

China has similarly bitter memories of Japanese wartime aggressions and is also at odds with Tokyo over sovereignty of an island chain in the East China Sea.

- 'A lot of baggage' -

"There's a lot of baggage, but all three countries acknowledge it's time to set that down for a while," said Kim Soung-Chul, an international policy expert at the Sejong Institute think-tank in Seoul.

"There are just too many common issues that need comprehensive discussion, and they are all under pressure at home and abroad to get this dialogue going again," Kim said.

No substantive breakthroughs are expected, although observers will be watching for any progress in efforts to seal a trilateral free-trade agreement.

Any such deal would provide a counterpoint to the new US-led Pacific trade pact of which China and South Korea are not members.

Park and Li met separately on Saturday, but the big sit down comes on Monday with the South Korean president's first summit with Abe.

Their meeting was only confirmed days before amid reports of behind-the-scenes bickering over how Japan's wartime sex slavery might be addressed.

"The summit is a big step forward for both countries," said Hideshi Takesada, a professor at Takushoku University in Tokyo.

"The South Korean side has pinned its hopes on a Japanese compromise over history and the so-called comfort women issue, but it is unlikely to resolve this during the summit.

"At best, the two sides would agree to continue their dialogue over the issue," Takesada said.