Mr. Xi Jinping didn’t refer to the U.S., although President Donald Trump has said trade pacts are a threat to American jobs and has decided to pull out of the Paris agreement.

Chinese President Xi Jinping on Tuesday warned that the world economy faces growing risks and uncertainties from countries turning inward on trade and resisting combating climate change, delivering an implicit rebuke to his American counterpart, Donald Trump.

Mr. Xi didn’t refer to the United States by name, although Mr. Trump has said trade pacts are a threat to American jobs and had decided to pull the U.S. out of the Paris agreement on climate change.

“Multilateral trade negotiations are having a difficult time. The implementation of the Paris Agreement on climate change is encountering resistance,” Xi told leaders of emerging economies and developing countries.

The agreement under which countries set their own national plans for cutting climate emissions went into effect in November.

“Some countries have become more inward—looking and less willing to take part in international cooperation, and the spillovers of their policy adjustments are deepening,” he said during a summit of BRICS nations, comprising Brazil, Russia, India, China and South Africa.

Mr. Xi’s criticism came at the opening of a dialogue between the leaders of BRICS countries and five other developing nations invited to take part in the discussions on the sidelines of the summit in the southeastern Chinese city of Xiamen.

On Monday’s opening day of the summit, the BRICS countries called for reform of the United Nations and tougher measures against terrorist groups, while denouncing North Korea’s latest nuclear test.

The five also pledged their opposition to protectionism, a theme increasingly taken up by Mr. Xi despite what critics say are substantial barriers to foreign investment in key Chinese sectors such as electricity generation and telecommunications.