President Barack Obama, trying to sway skeptics on free trade among his supporters, said Friday that if the U.S. can't come to terms on an accord being worked on with other Pacific nations, China will step in to fill the void.

Asia has the globe's most populous and fastest-growing markets and the U.S. has to have access to sustain economic growth, Obama said at a White House news conference with Italian Prime Minister Matteo Renzi.

"If we do not help to shape the rules so that our businesses and our workers can compete in those markets, then China will set up rules that advantage Chinese workers and Chinese businesses," he said.