US leader Joe Biden on Wednesday said he would ask President Xi Jinping about his "red lines" to reduce the potential for conflict amid soaring tensions over Taiwan when they gather next week in Bali.

A day before flying to Asia, Biden indirectly confirmed plans to meet Xi on the sidelines of the Group of 20 summit in what would be their first encounter since they became presidents of the world's two largest economies.

"What I want to do with him when we talk is lay out what kind of – what each of our red lines are," Biden told a news conference following US midterm elections.

Biden said he sought to know "what he believes to be in the critical national interests of China, what I know to be the critical interests of the United States, and to determine whether or not they conflict with one another."

If there are conflicts, Biden said he hoped to work together on "how to work it out."

The two leaders know each other unusually well for two presidents, with Biden in 2011 traveling to China to spend time with Xi when they were both vice presidents.

However, tension has risen sharply over Taiwan, with Biden having indicated on three occasions that he is ready to commit the US military to assist the island if the mainland launches an attack – a break with longstanding policy that was walked back each time by the White House.

Biden insisted on Wednesday that there was no change in the historic US stance of strategic ambiguity.

"The Taiwan doctrine has not changed at all from the very beginning," Biden said, adding that he would discuss Taiwan but also trade and China's relationship with other countries. (AFP)