BEIJING—Chinese President Xi Jinping warned Wednesday that confrontation between China and the U.S. would be a "disaster" for the world, as the two sides began high-level talks aimed at reversing a downturn in relations over the past year.

The two countries must "break the old pattern of conflict and opposition between great powers," Mr. Xi said at the opening of the annual U.S.-China Strategic and Economic Dialogue in Beijing.

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