President Trump is making his first official visit to China amid regional tensions on trade and North Korea.
Mr. Trump landed in Beijing Wednesday following a visit to South Korea.
He's scheduled to meet multiple times with China's President Xi Jinping during the two-day stay.
Xi was treating Mr. Trump to a lavish welcoming ceremony and tour of the Forbidden City, home to China's ancient imperial palaces.
The visit came hours after Mr. Trump addressed South Korea's National Assemblyand pressured China to stop supporting North Korea.
He also delivered a sharp warning to Pyongyang, telling the rogue nation: "Do not underestimate us. And do not try us."
In a speech delivered hours after he aborted a visit to the heavily fortified Korean demilitarized zone due to bad weather, Mr. Trump said he had a message for North Korean leader Kim Jong Un.
"The weapons you are acquiring are not making you safer, they are putting your regime in grave danger." He called on all nations to join forces "to isolate the brutal regime of North Korea."
"The world cannot tolerate the menace of a rogue regime that threatens with nuclear devastation," he said.
Mr. Trump made equalizing trade with China a centerpiece of his presidential campaign but has signaled that he may ease up in exchange for China's help with North Korea.
Mr. Trump arrived in Beijing with mounting U.S. trade complaints in the air, limiting prospects for progress on market access, technology policy and other sore points.
The strains between the world's two biggest economies are fueling anxiety among global companies and advocates of free trade that they could retreat into protectionism, dragging down growth.
Washington accuses Beijing of backsliding on market-opening promises, and Mr. Trump said last week that the U.S. trade deficit with China - $347 billion last year - is "so bad that it's embarrassing."
"I don't want to embarrass anybody four days before I land in China, but it's horrible," he said.
China is the third stop on Mr. Trump's ten-day Asia tour, which opened in Japan.