China and Vietnam on Monday signed dozens of cooperation agreements, strengthening ties between the two countries after President Xi Jinping warned that protectionism leads nowhere and that a trade war would have no winners.

Xi is in Vietnam for the first leg of a Southeast Asia tour, as Beijing tries to present itself as a stable alternative to an erratic US President Donald Trump, who announced – and then mostly reversed – sweeping tariffs this month.

President Xi was welcomed to Hanoi with a 21-cannon salute, a guard of honour and rows of flag-waving children at the presidential palace, before holding talks with Vietnam's top leaders including General Secretary To Lam.

The two neighbours signed 45 cooperation agreements, including on supply chains, AI, joint maritime patrols and railway development.

Xi's visit comes almost two weeks after the United States – manufacturing powerhouse Vietnam's biggest export market in the first three months of the year – slapped a 46 percent levy on Vietnamese goods as part of a global trade blitz.

Although the reciprocal tariffs on Vietnam and most other countries have been paused, China still faces enormous levies and is seeking to tighten regional trade ties and offset their impact during Xi's first overseas trip of the year.

Xi will depart Vietnam on Tuesday, travelling onwards to Malaysia and Cambodia on a tour that "bears major importance" for the broader region, Beijing has said.

Speaking during a meeting with Lam, Xi said Vietnam and China were "standing at the turning point of history... and should move forward with joint hands".

Xi earlier urged the two countries to "resolutely safeguard the multilateral trading system, stable global industrial and supply chains, and open and cooperative international environment".

He also reiterated Beijing's line that a "trade war and tariff war will produce no winner, and protectionism will lead nowhere" in an article published on Monday in Vietnam's major state-run Nhan Dan newspaper.

Vietnam's Lam said in an article posted on the government's news portal on Monday that his country "is always ready to join hands with China to make cooperation between the two countries more substantive, profound, balanced and sustainable". (AFP)