Admiral Harry Harris says every test, even it if fails, succeeds in bringing DPRK leader Kim Jong-un closer to his aspiration of being able to deliver nuclear warheads anywhere in the world.
A US Navy commander on Wednesday pushed for a "sense of urgency" over North Korea's nuclear and missile development, stressing that it even threatens Pyongyang's ally China and neighbour Russia.
Admiral Harry Harris, who heads the Pacific Command, spoke during a visit to Japan after the DPRK' latest ballistic missile test raised further alarm over the pace of its weapons development.
North Korea on Sunday launched what appeared to be its longest-range ballistic missile yet, claiming it was capable of carrying a "heavy nuclear warhead" in a test aimed at bringing the US mainland within reach.
Pyongyang carried out two atomic tests last year, and has accelerated its missile launch programme, despite tough UN sanctions aimed at denying leader Kim Jong-un the hard currency needed to fund his weapons ambitions.
Every test is a success
"In every test he [Kim] makes, it's a success because it takes North Korea one step closer to be able to deliver a nuclear-tipped missile anywhere in the world," Harris said.
"I must assume Kim Jong-un's claims are the truth, because I know his aspirations certainly are ... That should provide all of us with a sense of urgency to address this problem now," he added.
The United States said the missile landed close to Russian territory, but Moscow later said it fell in the ocean about 500 kilometres (310 miles) away and posed no threat.
Harris, however, stressed that ally China and neighbour Russia can no longer look the other way. It was a point that was also made by Nikki Haley, the US envoy to the United Nations.
"The dangerous behaviour by North Korea is not just a threat to the Korean peninsula ... it's a threat to China, it's a threat to Russia," Harris told an academic forum in Tokyo.
Russian President Vladimir Putin said the test was dangerous, but warned against attempts to "intimidate" Pyongyang.
Harris is visiting Tokyo to discuss North Korea and other issues with Japanese officials, including Prime Minister Shinzo Abe, whom he met on Tuesday.
He called for nations to "ratchet up sanctions" on the North, reiterating that the world needs to "bring Kim Jong-un to his senses, not to his knees."
After the missile launch on Sunday, the United States, Japan and South Korea called a UN Security Council meeting to press the DPRK to change course and dismantle its missile and nuclear programmes.
However, Pyongyang said its recent missile test-launch was a legitimate act of self-defence under international law and called US criticism a "wanton violation of the sovereignty and dignity of the DPRK."
North Korean diplomat Ju Yong-choi told the UN Conference on Disarmament on Tuesday, "The DPRK will bolster its self-defence capabilities as long as the United States continues its hostile policies towards the DPRK and imposes nuclear threats and makes blackmail."
Earlier this month the US, South Korea and Japan conducted naval exercises in the Sea of Japan, led by the aircraft carrier group of the USS Carl Vinson.
The US vessel is reportedly still in the region.