China’s premier, Li Qiang, the country’s second-highest-ranking official, made a spirited effort at the United Nations General Assembly in New York on Friday to shore up Beijing’s image on the global stage and contrast it with the disruptive policies of the Trump administration.

Mr. Li portrayed his country as a bulwark against the erosion of the values upon which the United Nations was founded and a force for global cooperation and multilateralism. “China has all along acted as a staunch defender of world peace and security,” he said.

“A major cause of the current global economic doldrums is the rise in unilateral and protectionist measures such as tariff hikes,” Mr. Li said, an apparent reference to the trade policies of the United States under Mr. Trump. By contrast, China had “consistently opened its door wider to the world,” he said.

Mr. Li’s comments and other efforts at the United Nations this week — including China’s first detailed public pledge to reduce greenhouse gas emissions — have continued Beijing’s effort to cast China as a leader of global institutions at a time of American retreat under Mr. Trump.

China has tried to seize on the unpopularity of America’s trade policy and U.S. support for Israel to drive a wedge between Washington and the rest of the world.

Beijing assigns great importance to the United Nations because the country wields major influence by holding one of five permanent seats on the Security Council. Beijing has often used that influence to marshal support from developing nations to cast votes in the U.N. General Assembly that align with its interests.