US President Donald Trump and Chinese counterpart Xi Jinping are expected to speak by phone on Tuesday, just hours after slapping tariffs on each other's economies in an escalating trade war.

Beijing said it was imposing levies on imports of US energy, vehicles and equipment in a return salvo minutes after Trump's threatened tariffs on Chinese goods came into effect.

Trump suspended tariffs on Mexico and Canada on Monday for a month after they vowed to step up measures to counter flows of the drug fentanyl and crossing of undocumented migrants into the United States.

Stock markets wavered on Tuesday as investors braced for volatile market activity in the coming weeks over Trump's threatened tariffs on the three biggest US trading partners.

"Let's see what happens with the call today," Trump trade advisor Peter Navarro, a veteran of the US president's first term, told news outlet Politico.

Asked if Trump could halt the tariffs on China too, he added: "It's up to the boss. I never get ahead of the boss, that's why I'm sitting here."

Trump imposed fresh 10 percent tariffs on Chinese goods, on top of levies that were already in place against America's biggest economic competitor. Mexico and Canada had faced 25 percent tariffs. 

White House Press Secretary Karoline Leavitt said on Monday that Trump was due to talk to Xi, but said Tuesday that "I don't have any updates on when that call will take place." 

"He is not going to allow China to continue to source and distribute deadly fentanyl into our country, that was the reason for this tariff," Leavitt told reporters outside the West Wing.

'Malicious'

China unveiled levies of 15 percent on imports of coal and liquefied natural gas from the United States, while crude oil, agricultural machinery, big-engined vehicles, and pickup trucks face 10 percent duties.

It says it will also probe US tech giant Google and the American fashion group which owns Tommy Hilfiger and Calvin Klein.

Beijing said the measures were in response to the "unilateral tariff hike" by Washington. It said it would also file a complaint to the World Trade Organization over the "malicious" levies.

It also unveiled fresh export controls on rare metals and chemicals including tungsten, tellurium, bismuth, and molybdenum, used in a range of industrial appliances.

China is a major market for US energy exports and according to Beijing customs data, imports of oil, coal and LNG totaled more than $7 billion last year.

But that is dwarfed by China's imports from more friendly powers such as Russia, from which it purchased $94 billion-worth last year.

Last-minute deals

Trump has made tariffs a key foreign policy tool of his second term, joking that the word tariff is the "most beautiful" in the dictionary.

The Republican billionaire said his tariffs aimed to punish countries for failing to halt flows of illegal migrants and drugs including the powerful opioid fentanyl into the United States.

Mexican President Claudia Sheinbaum and Canadian Prime Minister Justin Trudeau had both struck last-minute deals with Trump on Monday to tighten border measures, leading to a 30-day pause on threatened tariffs.

Talks will continue for the next month on broader deals.

Mexico said it had begun the 10,000-strong border troop deployment it had promised Trump as part of the agreement to halt tariffs.

"The deployment has already started," Sheinbaum told reporters.

More than 450,000 people have been murdered countrywide since Mexico launched a major offensive against drug cartels in 2006.

Trudeau meanwhile said Canada would appoint a "Fentanyl Czar" and list drug cartels as terrorist organizations.