New U.S. Ambassador to Japan William Hagerty emphasized Tuesday that relations between the two countries are "at the highest point," pledging Washington would protect Japan against any contingencies involving North Korea.

With Pyongyang's nuclear and ballistic missile ambitions threatening stability in the Asia-Pacific region, U.S. President Donald Trump and Japanese Prime Minister Shinzo Abe have a "special bond," Hagerty said in an interview with Kyodo News.

Businessman Hagerty back in Tokyo as U.S. ambassador

Abe's political instinct is "very solid," Hagerty said. "He made the first phone call to President Trump after the election. He made the first visit to the Trump tower...He made a big impression on the president."

"I do not believe there is another world leader that the president speaks with more often than Prime Minister Abe," said Hagerty, adding, "I think that coordination between our two governments is at the highest point in history."

Hagerty, who was a Tennessee businessman, presented his credentials to Emperor Akihito at the Imperial Palace late last month.

The new ambassador is known as a close ally of Trump as he served as a key member of the president's transition team.

Hagerty, meanwhile, built ties with Japan through a three-year posting in Tokyo from the late 1980s to early 1990s while working for the Boston Consulting Group, and in his work as commissioner of economic development for the state of Tennessee from 2011 to 2015.

Abe's government hopes that Hagerty will play a key role in deepening the Japan-U.S. alliance, as regional security has worsened recently against the backdrop of North Korea's provocations, including its latest nuclear test earlier this month.

"The president's instruction to me has to do with the Japan alliance," Hagerty said, adding that he has maintained close communication with the Abe administration and U.S. forces in and around Japan to enhance mutual cooperation.

"My charge is to maintain very close communications and to, in every case, make sure the Japanese public knows we are with Japan," he said.

Hagerty also expressed confidence in defense systems operated jointly by Washington and Tokyo, saying, "I would fully expect to see more interoperability moving forward with our systems."

The interview was conducted hours after the U.N. Security Council unanimously adopted a new sanctions resolution to impose the first restrictions on exports of crude oil and petroleum products to North Korea in punishment for its sixth and largest nuclear test on Sept. 3.

Pyongyang previously conducted a nuclear test in September last year and has continued to launch ballistic missiles in defiance of international warnings, including two intercontinental ballistic missiles into the Sea of Japan in July and one that flew over Japan into the Pacific Ocean late last month.

"We are sending an increasingly stronger message each time," Hagerty said, suggesting that the United States will continue putting more pressure on Pyongyang until the country takes concrete actions to abandon its nuclear weapons programs.

"Our goal is not to hurt North Korean people. Our goal is to send a message that we want the denuclearization of the peninsula," Hagerty said.

As for China's attempts to challenge Japan's administration of the Senkaku Islands, Hagerty said Article 5 of the Japan-U.S. security treaty "covers" the East China Sea islets, meaning that Washington will defend Tokyo in the event of conflict there.

"We acknowledge our responsibility under Article 5," Hagerty said. "We oppose any unilateral action in that area by any nation."

Regarding the plan to relocate the U.S. Marine Corps Air Station Futenma from a residential area in Ginowan to the less populated Henoko coastal district in Nago, both in Okinawa Prefecture, Hagerty said it should proceed.

Despite lingering protests from local residents in Japan's southern island prefecture, the relocation plan is "the solution that our two governments have agreed to," Hagerty said, adding, "It's the best plan we have."

The new ambassador succeeded Caroline Kennedy, who served under President Barack Obama's administration before leaving Tokyo in January.