Xi Jinping has urged Vietnam to resist “unilateral bullying” and uphold free and open trade, as he begins a high-stakes diplomatic tour of the region’s major export-reliant economies in a bid to position his country as a stable partner in contrast to the United States.

China's President Xi Jinping called on Monday for stronger ties with Vietnam on trade and supply chains amid disruptions caused by U.S. tariffs, as he attended the signing in Hanoi of dozens of cooperation agreements between the two communist-run nations.

Vietnam, historically a significant beneficiary of the "China +1" strategy, finds itself between pressure from the US and political ties with China. It was the first to engage in reciprocal tariff talks with the US, but was also featured in Chinese...