The international, sanctions-focused approach to dealing with North Korea has been a success, according to the commander of the U.S. Navy's Pacific Fleet, because it has staved off a war in Asia.

Speaking just three days after North Korea detonated a huge nuclear device that was or was close to being a hydrogen bomb, Adm. Scott Swift said that the only alternative to diplomacy and pressure was military action.

“I think that the strategy has worked,” Swift said in an interview Wednesday in Tokyo, describing the use of sanctions to try to stop North Korea from pursuing nuclear weapons. “I say it has worked because we are not at war.”

Swift reiterated recent pronouncements from the secretaries of defense and state that “all options are on the table” but that diplomacy and pressure were preferred to military action against North Korea.

The international community is in a “much better place” to deal with Pyongyang “than if we had foreclosed on the diplomatic options,” Swift said.

“China, South Korea, Japan, Russia, the United States — all of those with direct equities have been working hard,” Swift said after two days of meetings here and in Seoul with political and military leaders.

Since North Korea conducted its first nuclear test in 2006, it has been subject to increasingly harsh unilateral and multilateral sanctions, designed to cut off its ability to obtain the parts and the money needed for its weapons program but also to inflict so much economic pain that the current leader, Kim Jong Un, decides it’s not worth it.

But some analysts say the sanctions have clearly not worked, neither changing Kim’s calculus nor isolating the regime.

The nuclear test conducted Sunday had an explosive yield of 160 kilotons, the Japanese government said Wednesday, making it more than 10 times the size of the bomb that destroyed Hiroshima and putting it into thermonuclear territory.

Since Sunday's test, the United States has been pushing at the United Nations for "the strongest possible" sanctions against North Korea, raising the prospect of an oil embargo.

South Korea and Japan are backing the United States’ calls for more tough sanctions on North Korea, but China and Russia, both veto-wielding members of the U.N. Security Council, favor negotiations.

Russian President Vladimir Putin on Wednesday condemned the North’s latest nuclear test but dismissed the idea of cutting off oil exports to the communist country, which was once a Soviet client state and continues to have close ties with Moscow.

“It is clear that it is impossible to solve the problems of the Korean Peninsula by sanctions alone and pressure,” Putin said after talks with his South Korean counterpart, Moon Jae-in, at an economic forum in the Far Eastern Russian city of Vladivostok.

“One shouldn’t give in to emotions and drive North Korea into a corner,” Putin said, according to local reports. He added that the countries involved need to stop tensions from escalating.

“Without political and diplomatic tools, it is very difficult to change the situation” on the Korean Peninsula, Putin said.

Moon had asked the Russian president to support a drive to cut off crude oil supplies to North Korea, said Yoon Young-chan, Moon’s spokesman.

But Putin said that might hurt ordinary North Korean citizens, Yoon told reporters.

Elected president of South Korea in May on a pledge to engage with North Korea, Moon has taken a notably harder line in recent weeks, partly driven by Pyongyang's increasing provocations and partly, it seems, in response to President Trump's criticism Sunday of Moon's "talk of appeasement."

During a phone call Monday, Trump and Moon “agreed to maximize pressure on North Korea using all means at their disposal,” according to the White House.

Moon’s government said Wednesday it would go ahead with plans to install four more rocket launchers to complete the U.S. Terminal High Altitude Area Defense (THAAD) antimissile system at a base in the south of the country.

China's primary objection to an oil embargo stems from concern over stability on its borders. For all its anger with Kim over his nuclear and missile tests, Beijing does not want to cause the collapse of his regime and the uncertainty that would follow. For Russia, which has been under U.S. economic sanctions, resisting an oil embargo is more a matter of principle.

Still, Swift said that the focus on sanctions and diplomacy was a “glass half full” situation. “As long as we are not reaching into the military tool kit as the only option, then that’s a success,” he said.

Separately, Swift said he was taking steps to change the culture within the 7th Fleet after two fatal collisions at sea since June. A guided-missile destroyer, the USS Fitzgerald, collided with a container ship south of Japan in June, killing seven sailors, and another, the USS John S. McCain, collided with an oil tanker in August, leaving 10 sailors dead.

This came on the heels of two other incidents in the region involving 3rd Fleet guided-missile cruisers: a May incident in which the USS Champlain collided with a South Korean fishing vessel, and the USS Antietam’s running aground in Tokyo Bay in January.

After the fourth incident, Adm. John Richardson, chief of naval operations, ordered an operational pause so that the Navy could review procedures, and a separate investigation into how the Navy prepares its forces to operate in the Pacific.

Asked whether the collisions reflected a deeper problem with the culture inside the 7th Fleet, Swift said: “It does say something about it. That’s reflective of the reviews and the inspections that are ongoing.”

Swift fired Vice Adm. Joseph Aucoin as commander of the 7th Fleet after the USS McCain incident, although he had been due to retire in a few weeks.

“We’ve taken immediate steps to address the errors, but we also have to look at the culture,” Swift said. “You don’t change culture overnight, and you don’t change culture just by removing people. We have to change the approach people take to the challenges they face.”

The Fitzgerald, which is still in its home port of Yokosuka in Japan, will be moved to Mississippi next month for repairs, while the McCain, which is still in Singapore, will be brought back to Yokosuka while the Navy decides where it will be fixed.

Lee reported from Seoul. Yoonjung Seo in Seoul contributed to this report.

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