President Donald Trump said on Monday he will impose 10 percent U.S. tariffs on about $200 billion worth of Chinese imports, but he spared smart watches from Apple and Fitbit Inc and other consumer products such as bicycle helmets and baby car seats.

Trump, in a statement announcing the new round of tariffs, warned that if China takes retaliatory action against U.S. farmers or industries, "we will immediately pursue phase three, which is tariffs on approximately $267 billion of additional imports."

Collection of tariffs on the long-anticipated list will start September 24 but the rate will increase to 25 percent by the end of 2018, allowing U.S. companies some time to adjust their supply chains to alternate countries, a senior administration official said.