Trade ministers from many of the world's biggest economies vowed to broaden a deal to boost global trade Saturday, with the U.S. saying nothing is off-limits for discussion.

At a Swiss-hosted meeting on the sidelines of the World Economic Forum, ministers from China, the European Union, Japan, the U.S. and 15 other nations agreed to build on the "positive momentum" of a World Trade Organization summit last December in Bali where the organization's 159 member economies agreed to cut customs red tape.

The ministers agreed to address the most difficult remaining negotiating topics of agriculture, market access and services that eluded an agreement last month in the first WTO deal since the global trade body was formed in 1995, said Swiss Economics Minister Johann Schneider-Ammann, who hosted the meeting.