Japanese Prime Minister Shinzo Abe and South Korean Prime Minister Lee Nak Yon agreed Tuesday to work together toward the denuclearization of North Korea ahead of the third inter-Korean summit next week.

“I would like to express my respect for your country’s persistent efforts in seeking to improve South and North Korean ties and being a bridge between the United States and the North,” Abe said at the outset of the meeting in Vladivostok, held on the sidelines of a regional economic forum.

Abe also stressed the necessity of promoting their bilateral and trilateral cooperation also involving Washington in dealing with Pyongyang.

“South Korea has never forgotten the necessity of cooperation with the international community, including the United States and Japan, in realizing denuclearization and peace on the Korean Peninsula,” Lee said in response to Abe’s comments.

South Korean President Moon Jae In and the North’s leader Kim Jong Un will meet in Pyongyang on Sept. 18-20 as the United States and North Korea have reached an impasse in their negotiations on the North’s nuclear program following the historic summit between President Donald Trump and Kim in June.

Also Tuesday in Vietnam, Japanese Foreign Minister Taro Kono met with his South Korean counterpart Kang Kyung Wha as their countries are trying to keep in step with each other in responding to North Korea ahead of the planned inter-Korean summit.

During the meeting in Hanoi, Kang stressed the need for closer coordination to realize a denuclearized Korean Peninsula.

Abe and Lee reaffirmed the importance of their bilateral ties as this year marks the 20th anniversary of a joint declaration seeking to promote future-oriented relations, which was agreed by then Prime Minister Keizo Obuchi and South Korean President Kim Dae Jung.

They also took up the issue of “comfort women” forced to work in wartime brothels for the Japanese military, a thorny topic between the two neighbors, the Japanese Foreign Ministry said.

The ministry said Abe told Lee that Japan’s stance remains unchanged in seeking to implement a 2015 landmark bilateral accord aimed at “finally and irreversibly” resolving the decades-long issue. The ministry declined to provide Lee’s response to the comments by Abe.

The bilateral agreement included Japan providing South Korea with 1 billion yen ($9 million) fund to settle the matter.

But Moon’s government has said the deal, agreed under his predecessor Park Geun Hye, is not sufficient and has urged Japan to take additional steps.

President Moon, South Korea’s head of state and counterpart of Abe in the international arena, did not visit Russia despite Moscow inviting him to the Eastern Economic Forum in the Russian Far East port city.

The forum has been held since 2015 under Putin’s initiative aimed at attracting investment to the Far East region.

==Kyodo