Japan and China agreed Sunday to resume reciprocal visits by their leaders, underscoring that Asia’s two biggest economies are eager to mend ties in the year marking the 40th anniversary of the signing of a bilateral friendship treaty.

But the two sides apparently failed to find common ground on certain sensitive issues, including a territorial dispute, underscoring the need to focus on using their current momentum to improve relations.

Foreign Minister Taro Kono said he asked Chinese Premier Li Keqiang during their talks in Beijing to visit Japan as soon as possible to participate in a trilateral summit including South Korea that Tokyo wanted to host last year. Kono said Li replied “in a positive manner.”

The summit would bring Li to Japan for the first time since he took office in 2013.

Earlier in the day, Kono met with Chinese counterpart Wang Yi and State Councilor Yang Jiechi, the nation’s top diplomat.

During talks spanning more than three hours, Kono and Wang confirmed the importance of their leaders making mutual visits as part of a full-fledged push to improve Sino-Japanese relations, a Japanese government official said.

“We want to improve overall (bilateral) ties this year,” Kono, the first Japanese foreign minister to visit China in about two years, said at the outset of the meeting open to the media.

Kono, who arrived on Saturday, noted the importance of this year as Tokyo and Beijing mark the 40th anniversary of the peace and friendship treaty.

Wang responded by noting that China welcomes Japan’s “strong determination” to improve relations, while Yang told Kono that he “enthusiastically” welcomed the foreign minister’s visit to China.

All the meetings were held “in a positive and bright atmosphere,” Kono told reporters.

Prime Minister Shinzo Abe and Chinese President Xi Jinping have yet to make official visits to their respective countries. This has been due, in part, to the dispute over the Senkaku Islands, a group of uninhabited islets in the East China Sea known in China as the Diaoyu Islands. The tiny islets are administered by Tokyo, but also claimed by Beijing and Taipei, which calls them Tiaoyutai.

Tokyo and Beijing have been mired in a territorial row over the Senkakus for years. The dispute hit a fever pitch after the government led by then-Prime Minister Yoshihiko Noda, Abe’s predecessor, decided to effectively put them under state control in September 2012.

An increasing number of policymakers and scholars from Japan and China believe the renewed political stability in each country will create a better environment in which to promote practical cooperation.

Kono said North Korea’s ballistic missile and nuclear ambitions were on the agenda at the meeting, as Tokyo has urged Beijing to exercise its substantial leverage over Pyongyang and play a key role in forcing the country to change its policy.

Japan and China agreed to continue working together to bring about the denuclearization of the Korean Peninsula, Kono said, adding they also confirmed that they “won’t accept” Pyongyang as a nuclear power.

Meanwhile, Kono lodged a protest over the entry of a Chinese submarine into the contiguous zone around Japanese territorial waters near the Senkakus earlier this month, urging Beijing to take steps to prevent this from happening again.

Kono and Wang agreed to make efforts for the early implementation of a Maritime and Aerial Communication Mechanism in the East China Sea.

Japan called on China to avoid taking actions that could escalate tensions in the East China Sea, Kono said, adding China repeated its “own assertiveness” on the maritime issue.

“There are concerns between the two countries as we are neighbors,” Kono said. “But as the world’s second- and third-largest economies . . . we will manage them in a way that would not hurt friendly Japan-China ties.”

J. Berkshire Miller, a senior visiting fellow with the Japan Institute of International Affairs in Tokyo, said that although Beijing and Tokyo pledged to implement crisis management mechanisms in the East China Sea, “neither side has agreed to even the most baseline conflict-avoidance mechanisms.”

Chinese vessels and aircraft, Miller said, were likely to continue to enter the waters and skies surrounding the Senkakus as Beijing continues to diversify its blend of ships, aircraft and tactics in the East China Sea ﻿﻿ “through the employment of ‘gray zone’ tactics that look to gradually push boundaries without crossing red lines to provoke a united response from Japan and the U.S.”

These tensions, though, appear to have become a “normalized” part of the Sino-Japanese relationship, and bilateral ties look to be improving after both Abe and Xi bolstered their domestic power bases late last year.

In a sign of this improvement, the two nations reached an effective accord on a bilateral social security agreement that would eliminate dual pension payments by Japanese expats in China and vice versa.

Ahead of any Xi-Abe meeting could come a trilateral summit that also involves South Korea. Seoul hosted the previous trilateral meeting in 2015 and Tokyo has been due to host the next one, though a plan to hold it in 2016 was dropped amid political turmoil in South Korea that saw the country’s president at the time, Park Geun-hye, ousted.

The three countries have been rotating summit-hosting duties since 2008, although the gatherings were not held in 2013 and 2014 after a chill in Japan-China relations over the Senkaku dispute.

“While the trilateral summit would be positive, it really needs to be complemented with bilateral visits — ideally both in China and Japan,” said Miller.

Miller said that while a bilateral summit in China might occur before the year’s end, “the realization of a Xi Jinping visit to Tokyo remains a bit more aspirational.”

“Beijing is still holding out likely for some concession or summit achievement, such as progress toward Japan potentially joining the AIIB (Asian Infrastructure Investment Bank) or more concrete cooperation on the BRI (Belt and Road Initiative),” he said.

Kono’s trip to China was the first by a Japanese foreign minister since his predecessor, Fumio Kishida, visited in April 2016.

He was slated to return to Tokyo early Monday.