U.S. Defense Secretary Mark Esper has urged Japan to consider taking part in a coalition to protect shipping in the Strait of Hormuz as Washington struggles to garner support for its efforts to counter Iranian activities in the strategically key sea lane.

"Any and every country that has an interest in freedom of navigation and freedom of commerce needs to really consider (being) involved in this type of monitoring of the strait," he told reporters Tuesday en route to Tokyo where he was meeting with Japanese Prime Minister Shinzo Abe and Defense Minister Takeshi Iwaya.

"I think it's something that the Japanese should strongly consider. I'll be discussing this with them," he said.

Esper, who is on his first overseas trip since taking office last month, raised the issue in the meeting with Iwaya on Wednesday, according to a Japanese government source. He did not bring it up with Abe, Japanese Chief Cabinet Secretary Yoshihide Suga told a press conference.

Iwaya told reporters afterward that he explained Japan will think carefully about what role it can play in safeguarding ships in the Middle East, taking into consideration its oil needs and ties with both Washington and Tehran.

Enthusiasm for the plan among U.S. allies has been mixed. Britain and Israel have announced their willingness to participate, while Germany has declined.

In the meeting with Abe at the premier's office, Esper lambasted China for destabilizing the Indo-Pacific region, saying "their military aggression and calculated strategy of predatory economics violates the international rules-based order that we are trying to uphold."

His comments on China came a day after the United States designated the country as a currency manipulator, escalating their row that has played out through tit-for-tat tariffs.

He added that the United States remains committed to the "complete, irreversible and verifiable denuclearization of North Korea" and thanked Japan for its help in enforcing U.N. sanctions against the North.

Abe said that the Japan-U.S. security alliance has "never been stronger," a sentiment Esper echoed, calling it "ironclad" and crucial to a free and open Indo-Pacific region.

In his meeting later in the day with Iwaya, Esper said China is ignoring values such as the international rule of law, freedom of navigation and respect for the sovereignty of other nations.

Instead, China prefers "to coerce its neighbors into activities designed for Beijing's benefit," he said.

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The defense chiefs agreed on the importance of three-way cooperation with South Korea to address threats from North Korea, Iwaya told reporters, including an intelligence-sharing pact between Tokyo and Seoul that may be under threat amid growing enmity between the neighbors over trade policy and wartime history.

Seoul has suggested it may pull out of the bilateral General Security of Military Information Agreement, or GSOMIA, in response to Tokyo's tightening of export controls on some materials crucial to the South Korean technology industry.

The pact, signed in November 2016, allows the neighbors to share sensitive information regarding North Korea, which has launched what are believed to be short-range ballistic missiles four times in less than two weeks. A deadline to decide whether to renew it for another year comes later this month.

Esper, a Gulf War veteran and former executive at defense contractor Raytheon Co., became Pentagon chief on July 23, filling a seven-month void left by the resignation of his predecessor Jim Mattis.

He is on a tour of the Asia-Pacific region including Australia, New Zealand, Mongolia and South Korea. On Friday, he is slated to meet with South Korean Defense Minister Jeong Kyeong Doo in Seoul.