Nations that benefit from security provided by the United States need to "step up" as Washington takes risks and incurs costs in defending regions around the world, the U.S. ambassador to Japan said Wednesday.

"The president's desire is as we step up to have our allies step up with us" regarding security in Asia, William Hagerty told Kyodo News in an interview. The situation in the Strait of Hormuz "in my mind would be very similar. That as our risk, as our cost goes up to defend those regions, that other nations should also step up if they benefit," he said.

Bloomberg news agency reported earlier this week that U.S. President Donald Trump had mused to confidants about withdrawing from the Japan-U.S. security treaty, perceiving it as unfair as the U.S. pledge to protect Japan's security is not reciprocated.

Hagerty said he had never heard such comments by the president, who had rather emphasized the strength of the bilateral alliance.

"There is no change in the horizon from our perspective" about the defense treaty, he insisted. Washington wants U.S. allies to be aware that the security situation has changed and "to step up their commitments," he said.

In a Monday tweet, Trump questioned the U.S. military's presence in the Middle East to safeguard oil-shipping routes, saying major oil importers like China and Japan should be protecting their own ships in the Strait of Hormuz. The tweet came after two tankers, including one operated by a Japanese company, were sabotaged by unknown attackers near the strait.

Hagerty said it would be "fair" for nations to find ways "to support" the United States to keep commercial routes free but refused to specify how.

On North Korea, Hagerty refused to comment on the prospects of a third summit between Trump and North Korean leader Kim Jong Un, but said the United States wants "to keep the door open for negotiation" for the denuclearization of North Korea. He also said Japan can play "a significant role" to provide a "bright future" for North Korea because of its proximity, expertise and economic development.

Trump will keep raising the issue of Japanese citizens abducted by North Korea, making "our best effort to keep the door open to create the runway for Prime Minister Abe to bring this to a satisfactory conclusion for Japan," he said.

Hagerty acknowledged that the U.S.-China trade friction roiling the global market "has consequences" but the United States believes it is worth it in the long run.

"China would know what is required to get a deal done" after the United States and China had been very close to a deal, he said. Trump will meet his Chinese counterpart Xi Jinping on the sidelines of the Group of 20 summit in Osaka starting Friday.

Hagerty also justified U.S. calls on other nations to refuse Chinese 5G technology, saying not only was it a security concern but also an economic concern as state-owned enterprises could be a "real economic damper" if they were allowed to compete in a rapidly evolving technology market. Free market participants would be unwilling to commit capital to the market as it is hard to generate profits against state-owned enterprises, he added.

Hagerty also said it was possible for the United States and Japan to reach a breakthrough in trade negotiations and he expects something positive.

In their meeting in Tokyo in May, Abe and Trump agreed to speed up negotiations for a bilateral trade pact.