NEW YORK – Prime Minister Shinzo Abe, who became the first foreign national leader to meet face to face with U.S. President-elect Donald Trump on Thursday, hopes to produce an agreement to strengthen the Japan-U.S. alliance when they meet next time, according to informed sources.

To lay the groundwork for the next meeting, which will likely be held after Trump takes the oath of office in January, Abe plans to send officials to the United States for a series of talks with people close to the president-elect, said sources familiar with his thinking.

It is rare for a U.S. president-elect to hold talks with a Japanese prime minister before taking office. But Thursday’s informal talks, held at the real estate magnate’s Trump Tower residence in New York, was largely an introduction to substantive policy discussions in the months to come. Speaking to reporters after the meeting, Abe said he and Trump agreed to meet again when convenient.

“Our alliance does not work without mutual trust,” Abe told reporters. “Now, I know for sure that Mr. Trump is a credible leader.”

In a Facebook message, Trump said, “It was a pleasure to have Prime Minister Shinzo Abe stop by my home and begin a great friendship.”

Abe declined to disclose to reporters the details of his talks with Trump. “I communicated my basic thoughts on a range of issues,” he said.

Japanese government officials have been concerned over Trump’s election campaign rhetoric, which raised questions about the U.S. commitment to the alliance with Japan. For instance, he suggested the possible withdrawal of U.S. troops from Japan if Tokyo does not bear the full upkeep costs for them.

At their meeting, Abe is believed to have told Trump of the Japanese government’s belief that strengthening the Japan-U.S. security partnership, which constitutes a cornerstone of U.S. strategy for Asia, will serve the interests of the United States.

He is also likely to have underscored the importance of Japan and the United States spearheading efforts to create rules for trade and investment, after Trump pledged during his election campaign to pull his country out of the Trans-Pacific Partnership free trade agreement.

Aiming to build on the apparently smooth get-acquainted meeting between Abe and Trump and ensure a successful first bilateral summit next year, Japanese officials plan to increase contacts with U.S. personnel involved in foreign, security and trade policies in order to make the incoming Trump administration better informed of Japan’s policy attitudes, the sources said.

In Tokyo, members of the Abe Cabinet expressed hope for a deepening of the relationship between Abe and Trump after their first talks.

At a news conference on Friday, Deputy Prime Minister and Finance Minister Taro Aso noted that the Abe-Trump meeting lasted about 90 minutes, longer than scheduled.

“The longer-than-planned talks suggest they were on the same wavelength,” Aso said.

Chief Cabinet Secretary Yoshihide Suga said at a separate news conference, “It was a wonderful meeting that marked a big step forward in building a strong relationship of trust between the two leaders before the inauguration of the new (U.S.) administration.”

“We got off to a very good start,” Suga said.

In Beijing on Friday, China warned against strengthened bilateral ties that could hurt “third parties,” after the Abe-Trump talks.

“We hope that any cooperation and bilateral arrangements of relevant countries will not damage the interests of third parties,” Foreign Ministry spokesman Geng Shuang said, when asked about the talks.

Noting that China welcomes the “development of normal state-to state relations,” he also said that the security concerns of other countries should be respected and urged that any efforts be conducive to peace and stability in the region.

The comments marked China’s first official response to Abe and Trump’s talks, although the spokesman largely spoke in general terms, citing a lack of information on what the two had actually discussed.

China was likely to have been watching Abe’s talks with Trump closely.

Whether Trump’s administration will strengthen the U.S. military presence means much for China and Japan, whose bilateral relations themselves have been troubled for many years over a territorial dispute and their escalating regional rivalry.

Trump’s negative campaign statements about Japan made many officials in Tokyo worry about the future shape of their ties.

Some China watchers have pointed out to the likelihood of Beijing gaining more space to play a bigger role in Asia after Trump takes office in January.

At the same time, China is concerned about Japan taking a more independent defense policy, which could result in the enhancement of its military capabilities.

By JIJI, Kyodo