FUKUOKA, Japan — An unending trade war between the United States and China. President Trump’s weeklong threat to impose tariffs on Mexico. A potential clash with Europe over cars and agriculture.

Trade disputes spurred by the president’s affinity for employing tariffs as his diplomatic weapon of choice have cast a pall over the global economy as finance ministers gather in Japan for an annual Group of 20 meeting. The weekend of talks, beginning Friday evening in Fukuoka, is expected to be rife with friction as protectionism threatens to slow growth.

“Tension is rising with tariff increases and nontariff measures materializing in many parts of the world,” Taro Aso, Japan’s finance minister, said at an Institute of International Finance conference in Tokyo on Thursday.

A central figure in the discussions will be Steven Mnuchin, the Treasury secretary, who will again seek to reassure ministers from other countries about Mr. Trump’s trade agenda. All eyes will be on Mr. Mnuchin’s scheduled meeting with Yi Gang, the governor of the People’s Bank of China.