US President Donald Trump said on Sunday that he had spoken with Apple Inc's chief executive Tim Cook about the impact of US tariffs on Chinese imports as well as competition from South Korean company Samsung Electronics Co Ltd.

Trump said Cook "made a good case" that tariffs could hurt Apple, given that Samsung's products would not be subject to those same tariffs. Tariffs on an additional $300 billion worth of Chinese goods, including consumer electronics, are scheduled to go into effect in two stages on September 1 and December 15.

By contrast, the United States and South Korea struck a trade agreement last September.

"I thought he made a very compelling argument, so I'm thinking about it," Trump said of Cook, speaking with reporters at a New Jersey airport.

US stock futures rose upon opening on Sunday after Trump's comments. In addition to his comments on Apple, Trump said on Twitter earlier in the day that his administration was "doing very well with China."

Apple's MacBook laptops and iPhones would not face the additional tariffs until December 15, but some of the company's other products, including its AirPods, Apple Watch and HomePod, would be subject to the levies on September 1.

Apple was not immediately available for comment outside normal business hours.