Sri Lanka, April 24 -- China has sent back planes it ordered from the US in its latest retaliation over Trump tariffs, the boss of aircraft maker Boeing has said.

Kelly Ortberg said two planes had already been returned and another would follow after trade tensions between the two countries escalated.

Boeing's chief executive told CNBC that 50 more planes were due to go to China this year but their customers had indicated they will not take delivery of them.

The US put 145% tariffs on imports from China and it hit back with a 125% tax on US products.

Speaking in the Oval Office on Tuesday, Trump said he was optimistic about improving trade relations with China, saying the level of tariffs he had imposed would "come down substantially, bu...