What to know as President Donald Trump imposes steep new tariffs on imports from Canada, Mexico and China, prompting retaliation and countermeasures.

A growing number of countries, including American allies, are striking trade deals as the Trump administration erects a higher fence around its global commerce.

The president’s trade assault, which makes no distinction between ally and adversary, is an assertion of U.S. dominance with significant risks.

Wall Street opened lower after Trump's tariffs on Mexico, Canada and China, sparking fears of trade wars that'll slow economies and ignite inflation.

Robert Lighthizer, who was the U.S. trade representative in President Trump's first administration, says China poses an existential threat to the United States that must be urgently addressed by Washington.

U.S. President Donald Trump warned on Monday he might increase tariffs on China beyond the 10% he imposed on Saturday and that "we will speak to China" probably over the next 24 hours.

China's sharpest pushback on Sunday was over fentanyl, an area where the Biden administration had also been urging Beijing to crack down on shipments.

Officials in China have vowed unspecified countermeasures in what could become a trade war after President Trump’s proposed 10% tariffs on all Chinese goods. NBC News’ Janis Mackey Frayer reports from Beijing on China’s reaction.

The Chinese government threatened "countermeasures" against President Donald Trump's 10% tariffs, asserting that "Fentanyl is America's problem."

European leaders were bracing for U.S. tariffs after sweeping levies imposed by U.S. President Donald Trump, affecting billions of dollars in trade between Mexico, China and Canada, roiled global markets and currencies.