Chinese President Xi Jinping, seen on July 28 in Beijing, spoke to President Trump via phone on Friday. (Ng Han Guan/AP)

Chinese President Xi Jinping urged President Trump to exercise restraint over tensions with North Korea during a phone call Friday night, Chinese state media reported.

After a week of threats and counterthreats between Washington and Pyongyang, Xi urged both sides not to do anything that would aggravate tensions, China’s CGTN state television network reported.

But North Korea continued to fuel tension Saturday, with the Rodong Sinmun newspaper reporting that almost 3.5 million people, including students and retired soldiers, have asked to join or rejoin the North Korean military to fight against the United States over the latest sanctions it encouraged through the U.N. Security Council.

“All the people are rising up across the country to retaliate against the U.S. thousands of times,” said the newspaper, the mouthpiece of the ruling Workers’ Party. The report was almost certainly bluster rather than fact, but it showed that the North Korean regime is not backing down in the face of Trump’s threats.

Meanwhile, Japan finished installing surface-to-air missile interceptors in the western prefectures that North Korea said would be in the flight path of any missiles launched toward Guam, where North Korea is threatening an “enveloping strike.”

(Taylor Turner/The Washington Post)

In South Korea, the government began the environmental survey needed to complete the deployment of the Terminal High Altitude Area Defense (THAAD) missile defense system — a sign that the liberal government is now trying to expedite the deployment. 

In his phone call with Trump, Xi said China hoped the parties concerned would exercise restraint and refrain from taking any action that will aggravate tensions on the peninsula, according to CGTN. Dialogue, negotiations and a political settlement are the fundamental ways of solving the Korean Peninsula’s nuclear issue, Xi said during the call, which took place Saturday Beijing time.

“The Chinese leader expressed Beijing's willingness to maintain communication with the U.S. to appropriately resolve the Korean Peninsula nuclear issue,” the network reported.

Trump, who is scheduled to visit China later this year, on Tuesday threatened to respond to further threats from North Korea by unleashing “fire and fury like the world has never seen.”

Pyongyang in turn said it could strike the U.S. territory of Guam in the Western Pacific with ballistic missiles. In his latest salvos in the war of words, Trump said Friday that the U.S. military was “locked and loaded” and that North Korea would “truly regret it” if it attacked Guam.

China has viewed the rising tensions between Washington and Pyongyang with some alarm and has repeatedly urged dialogue to lower tensions. Although China supported stiffer United Nations sanctions last weekend after repeated North Korean missile tests, Chinese officials also want a restart of six-party talks, which stalled in 2009. Those talks would involve North and South Korea, the United States, China, Russia and Japan.

(Anna Fifield,Jason Aldag/The Washington Post)

The war of words has given China the chance to project itself as the voice of reason and restraint while others lose their heads. It argues that Washington’s long-standing belligerence toward North Korea helps explain why the regime has chosen to develop a nuclear weapons program — dodging its own responsibility for propping up the North Korean government.

Xi “stressed that China and the U.S. share the same interests on the denuclearization and peace on the Korean Peninsula,” CGTN said.

But China is deeply resistant to doing anything that could destabilize or topple the regime in Pyongyang. The Chinese government has worked to prevent a unified Korean state allied to the United States, going all the way back to the 1950-53 Korean War that saw hundreds of thousands of Chinese soldiers die. China remains North Korea’s major trading partner, providing the regime’s economic lifeline.

In an editorial on Friday, China’s state owned Global Times newspaper warned that China won’t come to North Korea’s aid if it launches missiles threatening U.S. soil and there is retaliation — but that China would intervene if Washington strikes first.

“China should also make clear that if North Korea launches missiles that threaten U.S. soil first and the U.S. retaliates, China will stay neutral,” the Global Times wrote. “If the U.S. and South Korea carry out strikes and try to overthrow the North Korean regime and change the political pattern of the Korean Peninsula, China will prevent them from doing so.”

As tension mounted this week, Japan prepared for the missile launches, which North Korea indicated could come this month.

Two events could provide triggers. North Korea on Tuesday will celebrate “Liberation Day,” marking Japan's defeat in World War II and the end of its colonization of the Korean Peninsula. Then the United States and South Korea on Aug. 21 will begin joint military exercises, drills that North Korea considers preparation for an invasion.

In announcing that it might simultaneously fire four intermediate-range ballistic missiles over western Japan toward Guam, North Korea listed the prefectures of Hiroshima, Shimane and Kochi as on the flight path.

The Maritime Self Defense Force, as Japan’s navy is known, already has Aegis destroyers ready to shoot down any missiles flying over, but the Air Self Defense Force on Saturday deployed Patriot Advanced Capability-3 missiles, which have a range of about 12 miles, to the areas Saturday in case the missiles come down over Japan.

“North Korea says it will target Guam, but it is possible that the missiles will fail to follow their programmed trajectories due to an error,” a government official said, according to the Asahi newspaper.

Meanwhile, the South Korean government on Saturday began a formal environmental survey about the THAAD deployment, which has been controversial in the southern rural area where it is stationed.

Liberal president Moon Jae-in, elected in May, had vowed to conduct an environmental review of the deployment, which he had questioned while on the campaign trail. But the events of the last few weeks, especially North Korea's firing of two intercontinental ballistic missiles last month, have caused Moon to do an abrupt about-turn and he now appeared to be in a hurry to approve the THAAD system.

Although this battery would not be able to shoot down long-range missiles, it is meant to protect South Korea from North Korean rockets aimed at them.

Fifield reported from Tokyo.  Shirley Feng contributed to this report.