TOKYO/BEIJING -- US President Donald Trump had separate phone conversations with Chinese President Xi Jinping and Japanese Prime Minister Abe on Monday and pledged closer cooperation with them amid the growing possibility of North Korea's nuclear or missile test.

"In today's telephone conversation, (we) completely shared the opinion that (the US and Japan) will continue to demand that North Korea refrain from provocative behaviors," Abe told reporters after his talks with Trump.

The US and Japan will jointly maintain high-level surveillance, Abe also said, referring to the countries' ongoing joint naval exercise involving the US aircraft carrier USS Carl Vinson, which was sent to the western Pacific to counter North Korea's military provocations.

Trump and Abe reportedly shared the possibility of North Korea venturing a nuclear test or a ballistic missile launch in celebration of the 85th anniversary of the founding of the Korean People's Army on Tuesday.

Shortly after the talks, Trump also spoke with Xi over the phone and agreed to closely discuss issues involving the Korean Peninsula, China's Xinhua news agency said.

The US and Chinese leaders pledged "close contact through various means to promptly exchange views on major issues of common concern," according to Xinhua.

Xi reportedly said China is decisively opposed to any behaviors running counter to UN Security Council resolutions, urging all the concerned countries to refrain from escalating tension on the peninsula.

The talks mark Trump's first phone conversations with both Abe and Xi on the same day and come as the North is alleged to be preparing its sixth nuclear test or a missile test. South Korean officials said Pyongyang is technically ready to detonate a nuclear device at any time.

As tensions heightened on the peninsula, Trump and Xi agreed in their first summit earlier in the month in the US to work closely together to convince North Korea to curb its nuclear program. 

The US has also directed the nuclear-powered aircraft carrier USS Carl Vinson to enter the waters off the peninsula later in the week.

North Korea's state-run news outlets have sniped at the aircraft carrier dispatch, pledging to sink it if the US triggers a war.

Amid the escalated tension, the chief nuclear envoys from South Korea, the US and Japan are to meet in Japan on Tuesday to chart ways to rein in North Korea's nuclear and missile threats.

Later in the day, China's foreign ministry appealed for composure by the concerned neighbors in dealing with "sensitive" North Korean issues.

"I want to make our principal stance clear although we would not need to comment on a hypothetical question," spokesman Geng Shuang said in a briefing after being asked about China's position in the event of a North Korean nuclear test on Tuesday.

"Currently, the situation on the Korean Peninsula is complex, sensitive and very tense," the spokesman said. "We strongly urge each concerned country to keep its composure and restraint and refrain from taking any action that could raise tension as there's a clear prohibition of the use of North Korea's nuclear and missile programs in UNSC resolutions."  (Yonhap)