Trump to discuss Iran war, but not Ukraine, at China summit

US President Donald Trump will discuss the Iran war with Vladimir Putin and Xi Jinping in the first ever three-way meeting between the leaders of the United States, Russia and China at a summit in Shenzhen next week but he is not expected to discuss Ukraine war, a US official said.

The three leaders will meet on the sidelines of the Asia-Pacific Economic Cooperation summit in the southern Chinese city, White House spokeswoman Olivia Wales told reporters.

"The president has made it clear that, among other topics, he will discuss the reduction of nuclear weapons in the world. This proliferation, President Trump believes, is very dangerous," Wales said.