If there is no deal at the end of the 90-day grace period, the US will increase tariffs on the US$200 billion of goods from 10 per cent to 25 per cent. The negotiations, and therefore the 90 days, can start immediately.

“President Trump and President Xi have agreed to immediately begin negotiations on structural changes with respect to forced technology transfer, intellectual property protection, non-tariff barriers, cyber intrusions and cybertheft, services and agriculture,” the White House said.

“Both parties agree that they will endeavour to have this transaction completed within the next 90 days. If at the end of this period of time, the parties are unable to reach an agreement, the 10 per cent tariffs will be raised to 25 per cent.”

Xi and Trump: a beginner’s guide to translating diplomatic speak

As part of the ceasefire deal, China agreed to buy a “very substantial amount of agricultural, energy, industrial, and other product from the United States to reduce the trade imbalance between our two countries. China has agreed to start purchasing agricultural product from our farmers immediately.”

However, the exact value of the purchases had not yet been agreed, the White House said.

Chinese Foreign Minister Wang Yi said China had agreed to import more US goods “according to its domestic market and people’s demands”, which will include “buying more products from the US to gradually address the trade imbalance”.

Wang also said that China would gradually solve the “legitimate concerns” of the US side, but did not elaborate.

Wang said the two sides would continue negotiations with the goal of “removing of all additional tariffs”.

Xi and Trump had “friendly and candid” talks over dinner and reached an “important consensus”, with China agreeing to buy more from the US to address the bilateral trade imbalance, the Chinese foreign minister said.

Dinner discussions about de-escalating tensions between the world's two largest economies lasted an hour longer than expected.

Both sides appeared satisfied at the end of the gathering, and applause was heard in the room as the dinner drew to a close.

Reuters reported that Trump hailed his agreement with Xi.

“It’s an incredible deal,” Trump said on Air Force One. “What I’d be doing is holding back on tariffs. China will be opening up. China will be getting rid of tariffs.”

He said that under the deal China would buy a “tremendous amount of agricultural and other product” from the United States. “It’ll have an incredibly positive impact on farming.”

In China, a commentary widely carried by state media and official government social media accounts, said China had subdivided 53 “structural issues” raised by the US into 142 items, and classified them as either “agreeable for mutual concession”, “negotiable” or “unacceptable”. It added that the US had also “positively addressed” what China considered “long overdue” issues unresolved by Washington.

G20 leaders reaffirm ‘rules-based international order’

In addition to trade, Trump and Xi discussed other issues, including the US opioid crisis and Taiwan. Xi agreed to designate fentanyl as a controlled substance, after complaints that inadequate regulations on pharmaceutical and chemical production were hampering America’s efforts to stem the flow of synthetic opioids from China.

The decision, which the US described as a “wonderful humanitarian gesture” and listed as the first item on the White House statement, means that those selling the drug to the US “will be subject to China’s maximum penalty under the law”.

Meanwhile, Wang said the US had agreed to stick to the one-China policy regarding Taiwan, although the White House’s statement did not mention the island.

The US has in the past acknowledged the one-China position without recognising Beijing’s sovereignty over Taiwan.

Beijing, which regards Taiwan as a breakaway province, views the island as a core interest and has warned the US against supporting pro-independence forces and demanded that it cut off military exchanges.

China also expressed support for Trump meeting North Korean leader Kim Jong-un for a second time, with Wang adding that the US had expressed its appreciation of China’s role in helping to push the North towards denuclearisation.

The trade deal also gave new hope to a potential merger of semiconductor firms.

Xi said he was “open to approving” the acquisition by US semiconductor firm Qualcomm of Dutch chip maker NXP, according to the White House statement. China had blocked the deal on antitrust grounds after and US and European officials had approved it. Qualcomm abandoned the proposed purchase after China rejected it, so it is unclear whether it would resume interest in the deal even if China were to reverse its position.

Amid reports of the US tightening its visa policy for Chinese scholars and students, Xinhua quoted Trump as saying to Xi that the US welcomed Chinese students studying in America.