China’s President Xi Jinping moved to calm growing tensions over North Korea, telling U.S. leader Donald Trump in a phone call that all sides should maintain restraint and avoid inflammatory comments.

Xi’s comments, reported by China’s CCTV, came shortly after Trump added to his recent aggressive tweets by saying that U.S. military options were “locked and loaded” if North Korean leader Kim Jong Un acted unwisely. China is North Korea’s main benefactor, providing most of its food and fuel.

The White House said that Trump and Xi agreed that North Korea must stop provocative behavior, reiterating their mutual commitment to rid the Korean peninsula of nuclear weapons. It also said that Trump looked forward to visiting China later this year, calling the relationship between the two leaders “extremely close.”

The warm words exchanged Friday night in the U.S. masked underlying tensions between Beijing and Washington over how to deal with the errant regime in Pyongyang. Trump has often used sharp words to argue that China isn’t doing enough to rein in North Korea, and has threatened punitive measures on trade if Xi fails to act.

China, on the other hand, is reluctant to put so much pressure on the regime that it risks collapse. While North Korea is testing the patience of its longtime benefactor, such a scenario could lead to a unified Korea and push U.S. troops right up to its border.

China’s dilemma was on display in an editorial published on Friday by the Communist Party-affiliated Global Times. The newspaper said that Beijing should stay neutral if North Korea provoked the Trump into war with a missile attack. At the same time, it said that China would intervene if the U.S. and South Korea sought to attack North Korea and topple his regime.

China agreed to harsh United Nations sanctions earlier this month even while calling on all sides to take a step back and negotiate a solution. Formal talks on North Korea’s nuclear program collapsed in 2009, and Kim has accelerated his efforts to obtain the ability to strike the U.S. with a nuclear weapon.

The Trump-Xi phone call came as Japan set up a missile-defense system in western areas of the country, following a threat by North Korea to fire missiles over Japan toward the U.S. territory of Guam. The deployment of four Patriot interceptors was expected to be completed Saturday, a spokesman for Japan’s Ministry of Defense said by phone. He asked not to be named.

Japanese Prime Minister Shinzo Abe told local media earlier on Saturday that he would “do his best” to protect the lives and property of his fellow citizens.

New Phase?

South Korea hopes the talks between Trump and Xi will be an opportunity to ease the high tensions and shift the situation into a new phase, South Korea’s presidential Blue House was quoted as saying by the Yonhap news agency.

The European Union’s Political and Security Committee will meet Monday in an extraordinary session called by foreign policy chief Federica Mogherini to discuss “possible next steps” on North Korea, according to an emailed statement.

Trump has stepped warnings that Kim’s regime would face a devastating military strike if it continued threatening the U.S. On Friday, he said that if Kim makes any “overt threat” or strike at a U.S. territory or ally “he will truly regret it and he will regret it fast.” Trump also said the U.S. was considering tighter sanctions against North Korea.

“Hopefully it will all work out,” he told reporters in Bedminster, New Jersey. “Nobody loves a peaceful solution better than President Trump.”

Brink of War

North Korea’s state-run Korean Central News Agency accused Trump earlier of moving the Korean Peninsula “to the brink of a nuclear war.” The U.S. hasn’t taken any public steps to prepare for hostilities such as evacuating Americans from Seoul, which is within range of North Korean artillery, or moving ships, aircraft or troops into position for an imminent response.

After a week of tumult, financial markets began to stabilize on Friday. The S&P 500 Index rebounded from its steepest drop since May, and the CBOE Volatility Index dropped 3.3 percent, after Thursday’s 44 percent spike.

Terence Roehrig, a national security affairs professor at the U.S. Naval War College in Newport, Rhode Island, said Trump’s posture suggested he was trying to dissuade Kim from further provocations rather than setting the stage for a U.S. military strike.

“The president’s rhetoric could be aimed at China, but largely it is aimed at North Korea, trying to deter,” Roehrig said. “North Koreans are not suicidal. They may continue launching missile tests but they don’t want a war, and the U.S. doesn’t want military action either. ”