TOKYO (Reuters) - Japanese Prime Minister Shinzo Abe plans private personal meetings with Philippine President Rodrigo Duterte in Tokyo next week, three sources said, seeking to keep him onside with U.S.-led efforts to contain Beijing’s South China Sea ambitions.

Japan's Prime Minister Shinzo Abe shakes hand with Philippines President Rodrigo Duterte while Laos Prime Minister Thongloun Sisoulith looks on during the ASEAN-Japan Summit in Vientiane, Laos September 7, 2016. REUTERS/Soe Zeya Tun

With Duterte winding up a trip to China where he announced his “separation” from the United States, Abe faces a delicate task to promote the closely aligned security goals of Tokyo and Washington without pushing the Philippine leader deeper into Beijing’s embrace.

“Japan wants to explain its regional stance, including its thinking regarding the South China Sea,” said one of the sources. “Abe wants to make a connection with Duterte,” he added, asking not to be identified because he is not authorized to talk to the media.

Duterte’s apparent cosying up to Beijing has both Tokyo and Washington worried that the commitment under former Philippine President Benigno Aquino to stand up to China in the hotly disputed waterway is under threat.

Aquino angered China by lodging a case with an arbitration court in the Hague challenging the legitimacy of Beijing’s maritime claims in the resource-rich sea.

The ruling earlier this year emphatically favored Manila but was rejected by China, which has repeatedly warned the United States and Japan to stay out of the dispute.

On Friday, Chinese Foreign Ministry spokeswoman Hua Chunying said Japan was “sparing no effort” to get involved in the South China Sea issue, saying Japan was behind the times in the rapidly improving China-Philippines relationship.

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Abe will hold one-on-one talks with Duterte at his residence in Tokyo on Wednesday night following a larger, more formal meeting with senior officials, the sources said.

“It’s unusual for the Japanese prime minister to hold a second smaller meeting,” another of the sources said.

Japanese Foreign Minister Fumio Kishida will also host Duterte for an informal dinner on Tuesday.

Duterte visited Beijing first with an entourage of around 200 business people. On Thursday, he declared the United States had lost and he had “realigned” with China.

Duterte has railed against U.S. criticism of his deadly war on drugs and called President Barrack Obama a “son of a bitch” but has so far maintained cordial ties with U.S. ally Japan.

“Right now Japan seems determined to cultivate a relationship with him and will avoid the hot-button topics (eg human rights) lest Duterte also junk them as well,” said one of the sources.

Japan wants to confirm the importance of the rule of law and freedom of navigation, a Japanese government official told Reuters. It’s unlikely, however, that Abe will try to intervene in Duterte’s spat with Washington or discuss the Hague ruling, he added.

Duterte places “great value on the Philippines’ vibrant and dynamic relationship” with Japan, a Philippine government spokeswoman said ahead of the visit.

Chief Cabinet Secretary Yoshihide Suga said Tokyo was looking at how the developments between China, the Philippines and the United States might affect Japan but would not comment.

“In regard to the problem in the South China Sea, we are looking reach a diplomatic solution through cooperation between with the countries involved,” Suga told a regular media briefing on Friday.

Japan in June committed itself to a bigger security role in Southeast Asia when then Minister of Defence Gen Nakatani said his country would help nations such as the Philippines and Vietnam build their security capabilities to deal with “unilateral, dangerous and coercive actions” in the South China Sea.

“There is more Chinese assertion in the South China Sea and Japan has more worries it will do the same the same in the East China Sea,” said Alison Evans, deputy head of Asia Pacific Desk, Country Risk at IHS Markit. “Japan has to be more concerned now than six months ago.”

On Wednesday, Abe will sign an agreement to supply two new patrol boats to the Philippines, the sources said, adding to the vessels and aircraft Japan has already provided to help keep tabs on activity in the South China Sea.

Duterte and his entourage will then meet leaders from companies including Toyota Motor Corp 7203.T and Mitsubishi Motors 7211.T to seek further investments in the Philippines.

Duterte concludes his trip on Thursday with a call on Japan’s Emperor Akihito.