The incoming U.S. administration's tough talk against China has set the stage for showdowns on everything from security to trade and cyberspace, but contradictory signals are sowing uncertainty over how far President-elect Donald Trump is prepared to go in confronting Beijing.

Highlighting the contested South China Sea as a potential flash point, Trump's secretary of state nominee Rex Tillerson threw out an explosive challenge to Beijing on Wednesday by calling for it be denied access to artificial islands it is building in the strategic waterway.

A Trump transition adviser said that Tillerson, Trump's pick to be America's top diplomat, did not mean to suggest the new administration would impose a naval blockade, which would risk armed confrontation with China, something the new administration was not seeking.