Efforts to complete the world's largest trade deal were pushed back to next year as ministers failed to agree on key issues at a Singapore summit.

Negotiations on the Regional Comprehensive Economic Partnership (RCEP) — covering half the world's population and excluding the United States — are expected to be completed in 2019, Chinese Premier Li Keqiang said Tuesday in Singapore. The previous plan was to reach a "substantial conclusion" this year.

The Asia-Pacific RCEP project is running into headwinds facing the global economy. “In the context of rising protectionism and setbacks for free trade, advancing the WTO rules-based RCEP would not only benefit people in the region, but also send the world a strong signal of upholding and promoting free trade,” Li said.

The RCEP countries include China, Japan, South Korea, India, Australia, New Zealand and the 10 members of the Association of Southeast Asian Nations.