Asian markets rose on increasing optimism that the two sides would be able to hammer out a deal ahead of a March deadline and avert further import tariff hikes.
"Talks with China are going very well!" Trump tweeted after the second day of negotiations on Tuesday.
The US delegation, led by Deputy Trade Representative Jeffrey Gerrish, was supposed to end its visit on Tuesday.
Washington has been clamouring for an end to the alleged forced transfer -- and even theft -- of American technology, as well as steep government subsidies for Chinese companies.
Neither Chinese nor US officials have given any details about the discussions.
"I don't speak for them obviously," Cook said in reference to the Trump administration.
"I do talk with them and I give them my ideas and thoughts."
The US smartphone maker has felt the pinch of the bruising trade spat, and warned that 2018 revenues would miss its forecast -- in large part due to a slump in iPhone sales in China.
The temporary ceasefire came after the two sides imposed import duties on more than USD 300 billion of each other's goods.
Without a resolution, punitive US duty rates on USD 200 billion in Chinese goods are due to rise to 25 per cent from 10 per cent on March 2.
The current trade round coincided with an unannounced visit from North Korean leader Kim Jong Un, who arrived in Beijing on Tuesday for talks with Xi in Beijing ahead of a possible second meeting between Kim and Trump.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)