Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping agreed Friday to closely cooperate in resolving the North Korean nuclear and missile issues, while confirming the importance of U.N. sanctions against the North to achieve that goal.

In the first telephone talks between a Japanese prime minister and Chinese president, which signals improving relations between Asia's two biggest powers, Abe and Xi welcomed the commitment recently expressed by North Korean leader Kim Jong Un and South Korean Moon Jae In toward a "complete" denuclearization of the Korean Peninsula.

Abe and Xi also agreed to cooperate toward an early resolution of the issue of Japanese nationals abducted by North Korea in the 1970s and 1980s, a senior Japanese government official said.

The promise by Xi to cooperate on the long-stalled abduction issue comes as positive news for Abe amid concerns Japan has been left behind by recent diplomatic moves related to North Korea. Abe has said the abduction issue is one of his government's top priorities.

The telephone talks were held at Japan's request, with Tokyo eager to win Xi's cooperation in addressing the North Korea issues. China is a major ally of North Korea and Xi met with Kim on March 26 ahead of the historic inter-Korean summit on April 27.

Chinese broadcaster CCTV said Xi told Abe he hopes Japan will play constructive roles, saying he wants to resolve the North Korean issues through dialogue and in a balanced manner by taking into account the interests of related countries.

To ensure the enforcement of U.N. sanctions on North Korea, Abe and Xi confirmed they will address Pyongyang's attempts to evade the sanctions through means such as ship-to-ship transfer of goods at sea, the official said.

Japan has noted and reported to the United Nations multiple cases of the suspected ship-to-ship goods transfers between North Korean and foreign-registered tankers in the East China Sea since January.

The 40-minute phone talks came before a summit between Japan, China and South Korea on Wednesday in Tokyo, and before U.S. President Donald Trump meets with Kim in the coming weeks for the first U.S.-North Korea summit.

Abe has expressed his desire to visit China and realize a reciprocal trip to Japan by Xi. They agreed Friday to further deepen bilateral relations, which in recent years have been strained by territorial and historical issues.

"We agreed to heighten Japan-China relations...to the next stage by significantly expanding public exchanges in various areas" with this year marking the 40th anniversary of the signing of a friendship treaty between the two countries, Abe told reporters.

The prime minister underscored the significance of the telephone talks, telling the Chinese president, "It's productive that I can directly exchange views with (you) at a time when the situation over North Korea is evolving greatly," according to the Japanese official.

Xi also told Abe the telephone talks are a demonstration of the recent forward-looking change in the bilateral relationship, the official said.

The upcoming trilateral summit is to be attended by Abe, Moon and Chinese Premier Li Keqiang. Abe is expected to hold bilateral talks with Li and Moon on the sidelines.

Also Friday, Xi and Moon agreed by telephone to cooperate to replace the Korean War armistice with a peace treaty and to communicate closely toward the success of the North Korea-U.S. summit, the office of the South Korean president said.

Xi told Moon that formally declaring an end to the 1950-1953 Korean War will end hostilities on the divided peninsula, the office said.