Donald Trump and Shinzo Abe have agreed to take fresh action against North Korea as they pledged to take "all necessary measures to protect allies” from the nuclear-armed state.
The US President and Japanese Prime Minister held a telephone call on Monday and agreed on the need for more measures aimed at curbing the country’s military ambitions, just hours after America’s ambassador to the United Nations said Washington was "done talking about North Korea".
Mr Abe told reporters after his conversation with Mr Trump on Monday that repeated efforts by the international community to find a peaceful solution to the North Korean issue had yet to deter Pyongyang.
"International society, including Russia and China, need to take this seriously and increase pressure," he said.
Mr Abe added that he backed Mr Trump's "commitment to taking all necessary measures to protect allies".
The pair did not discuss military action against North Korea, nor what would constitute the crossing of a "red line" by Pyongyang, Deputy Chief Cabinet spokesman Koichi Hagiuda said.
A White House statement after the phone call said the two leaders "agreed that North Korea poses a grave and growing direct threat to the United States, Japan, the Republic of Korea, and other countries near and far".
It said Mr Trump "reaffirmed our ironclad commitment" to defend Japan and South Korea from any attack, "using the full range of United States capabilities".
Japan's Chief Cabinet Secretary Yoshihide Suga said the talk between Mr Abe and Mr Trump lasted for about 50 minutes.
"The role that China can play is extremely important," he told a news conference.
"Japan intends to call on those countries involved - including the UN, the United States and South Korea to start, but also China and Russia - to take on additional duties and actions to increase pressure," he said.
North Korea said on Saturday it had conducted another successful test of an intercontinental ballistic missile that proved its ability to strike the US mainland, drawing a sharp warning from Mr Trump and a rebuke from China.
The US President later wrote on Twitter that he was "very disappointed" in China.
State-run Chinese newspaper the Global Times said in an editorial on Monday that Mr Trump's "wrong tweet" was of no help, and that the President did not understand the issues.
"Pyongyang is determined to develop its nuclear and missile programme and does not care about military threats from the US and South Korea. How could Chinese sanctions change the situation?" said the paper, which is published by the ruling Communist Party's official People's Daily.
South Korean President Moon Jae-in, who is on holiday, planned to have a phone call with MR Trump soon, a senior official at the Presidential Blue House said.
The United States flew two supersonic B-1B bombers over the Korean peninsula in a show of force on Sunday in response to the missile test and the 3 July launch of the "Hwasong-14" rocket, the Pentagon said.
The bombers took off from a US air base in Guam and were joined by Japanese and South Korean fighter jets during the exercise.
"North Korea remains the most urgent threat to regional stability," Pacific Air Forces commander General Terrence J. O'Shaughnessy said in a statement.
"If called upon, we are ready to respond with rapid, lethal, and overwhelming force at a time and place of our choosing."
Nikki Haley, US Ambassador to the United Nations, said in a statement China must decide if it is willing to back imposing stronger UN sanctions on North Korea over Friday night's long-range missile test, the North's second this month.
Any new UN Security Council resolution "that does not significantly increase the international pressure on North Korea is of no value", she said, adding that Japan and South Korea also needed to do more.