China's President Xi Jinping told Spanish lawmakers on Wednesday his country would boost protection of intellectual property ahead of a G20 meeting where he faces a trade showdown with the United States.

Xi is due to meet his US counterpart Donald Trump at the gathering in Argentina this week, with Washington threatening to ramp up a trade war with Beijing if it doesn't allay US concerns over intellectual property theft and China's forced technology transfers.

“China will make efforts to further open its door to the outside world,” Xi told the Senate as he pays a state visit to Spain.

“We will make a lot of efforts to speed up market access, improve the investment environment and increase protection of intellectual property.”

US has already imposed tariffs on more than $250 billion in Chinese goods in an attempt to pressure the country to reverse its alleged unfair trade practices.

Washington this week warned it might impose tariffs on its remaining $267 billion in imports from the Asian giant, including iPhones made in China.

The issue will take centre stage at the G20 meeting in Argentina, which starts on Friday.

Xi also warned that the world faced “unprecedented” instability and uncertainty. He said that in economic terms, this centred on “whether or not we will continue economic globalisation and free trade, or if we turn to unilateralism and protectionism".

Xi has cast himself as a defender of globalisation and opponent of protectionism, but US and European governments say foreign companies still face many hurdles to do business in the Communist-ruled country.