A week before the third summit between the two Koreas in five months begins in Pyongyang, Chinese President Xi Jinping, Japanese Prime Minister Shinzo Abe and South Korea's Prime Minister Lee Nak-yeon converge on Vladivostok for an economic forum held September 11-13.

The event in the far eastern Russian city is symbolic of Moscow's push for closer diplomatic and economic ties with Asia as its relations with the West are in crisis.

It will also allow the Kremlin to discuss the dramatic rapprochement between Trump and Kim Jong Un with key regional players.

Kim was also invited to the Vladivostok forum but will not attend, a Russian lawmaker said at the weekend.

Japan's Abe is set to meet Putin on Monday evening to discuss "boosting economic cooperation and commercial exchanges" but also to "exchange views on the situation on the Korean peninsula," said Russian presidential adviser Yuri Ushakov.

Talks with China's Xi -- the third meeting this year -- are planned for Tuesday, and a meeting with Lee Nak-yeon Wednesday.

Russia and China both have land borders with North Korea and were its allies in the Korean conflict in the early 1950s.

They support North Korea's denuclearisation and abide by international sanctions against Pyongyang, but have rejected Trump's threats of military action made last year.

A week after the leaders meet Putin, a summit of the two Koreas will take place in Pyongyang on September 18-20.

Seoul is currently looking to give second wind to diplomatic momentum that culminated in the historic summit between Kim Jong Un and Trump on June 12 in Singapore.

The two reached the vague compromise in favour of "complete de-nuclearisation of the Korean peninsula", but no timeline and details were agreed.

- Moscow's second fiddle -

Since the summit, diplomatic negotiations between the two countries have seemed to stall, and Trump in August cancelled a planned visit to Pyongyang by Secretary of State Mike Pompeo.

If South Korea opts to normalise ties with Pyongyang despite the cooling of Washington's enthusiasm, it will need diplomatic support in the region, said political analyst Fyodor Lukyanov.

Though Moscow has never played a leading role on the issue, "this is where Russia's role would become centre stage," he said.

And the issue of nuclear-armed North Korea will most likely not be the main topic in Vladivostok, said Andrei Lankov, a historian at Seoul's Kookmin University.

Unlike China, Russia "has not given any financial aid to Pyongyang for over 30 years," its support to North Korea is "purely symbolic," so it does not have any real leverage for influence in the country.

Since the beginning of the year, Kim Jong Un has made three visits to China, met once with Trump and twice with South Korean President Moon Jae-in, "and he did not meet Putin once," Lankov noted.

Unlike his predecessor Kim Jong-il, the current North Korean leader has never been to Russia.

Sooner or later, Kim will end up coming to Russia, Lankov said, but "like Trump, he likes dramatic effects, and he will monitor to see when his visit would make the biggest impact possible".