President Donald Trump has again made separate telephone calls from the White House to the leaders of Japan and China to discuss concerns about North Korea.
The 30-minute call between Trump and Japanese Prime Minister Shinzo Abe was meant to increase pressure on Pyongyang not to engage in further provocative actions, but was not prompted by any significant change in the situation, according to officials in Tokyo.
"We agreed to strongly demand North Korea, which is repeating its provocation, show restraint," Abe told reporters in Tokyo on Monday.
"We will maintain close contact with the United States, maintain a high level of vigilance and firmly respond," he added.
Abe also said he and Trump agreed that a larger role in dealing with Pyongyang should be played by China.
Trump subsequently spoke to Chinese President Xi Jinping about North Korea, according to the official Xinhua news agency.
The Chinese president, on the call, said he hopes all sides avoid doing anything to worsen the tense situation on the Korean peninsula, according to the news agency.
White House officials earlier on Sunday had confirmed to VOA News the calls to Abe and Trump would be made but they released no immediate details.
U.S. officials have repeatedly said all options remain "on the table" to deal with further North Korean provocations.