The United States and China reached a 90-day ceasefire in a trade dispute that has rattled financial markets and threatened world economic growth.

The breakthrough came after a dinner meeting on Saturday between US president Donald Trump and Chinese leader Xi Jinping at the G20 in Buenos Aires.

Mr Trump agreed to hold off on plans to raise tariffs at the start of 2019 on 200 billion dollars (£155 billion) in Chinese goods.

The Chinese agreed to buy a “not yet agreed upon, but very substantial amount of agricultural, energy, industrial” and other products from the United States to reduce America’s huge trade deficit with China, the White House said.

The truce, reached after a dinner of more than two hours, buys time for the two countries to work out their differences in a dispute over Beijing’s aggressive drive to supplant US technological dominance.

“It’s an incredible deal,” Mr Trump told reporters aboard Air Force One.

“What I’ll be doing is holding back on tariffs. China will be opening up, China will be getting rid of tariffs. China will be buying massive amounts of products from us.”

In a long-sought concession to the US, China agreed to label fentanyl, the deadly synthetic opioid responsible for tens of thousands of American drug deaths annually, as a controlled substance.

The White House announcement framed a victory for Mr Trump and his unflinching negotiating tactics, securing a commitment from China to engage in talks on key US economic priorities, with little obvious concession by the US.

Notably, however, the White House appears to be reversing course on its previous threats to tie trade discussions to security concerns, like China’s attempted territorial expansion in the South China Sea.

The Trump-Xi meeting was the marquee event of Mr Trump’s whirlwind two-day trip to Argentina for the G-20 summit after the president cancelled a sit-down with Russian President Vladimir Putin over mounting tensions between Russia and Ukraine.

The United States and China are locked in a dispute over their trade imbalance and Beijing’s tech policies.

Washington accuses China of deploying predatory tactics in its tech drive, including stealing trade secrets and forcing American firms to hand over technology in exchange for access to the Chinese market.

Mr Trump has imposed import taxes on 250 billion dollars (£195 billion) in Chinese products — 25% on 50 billion dollars worth and 10% on the other 200 billion.

Under the agreement reached in Buenos Aires, the two countries have 90 days to resolve their differences over Beijing’s tech policies.

If they cannot, the higher US tariffs will go into effect on the 200 billion dollars in Chinese imports.

He said there were three sites under consideration, but he declined to name them.

Mr Trump also said he would shortly be providing formal notice to Congress that he will terminate the North American Free Trade Agreement, giving politicians six months to approve the replacement he signed on Friday.

He said they can choose between the replacement, the United States-Mexico-Canada Agreement, or nothing.