Trump gave no details about the auto tariffs, and there was no immediate response from the Chinese government.
President Donald Trump and top US officials said on Monday that a trade truce with China will lead to structural changes in Beijing's economic policies, including lower tariffs, lower non-tariff barriers and more market access for USA companies.
"My relationship is very special, the relationship that I have with President Xi", he said as the two men were seated.
Had a deal not been struck, tariffs on US$200bn worth of Chinese goods would have risen from 10% to 25% at the start of 2019.
US Trade Representative Robert Lighthizer said last week that he was examining all available tools to raise US tariffs on Chinese vehicles to the 40 percent level that China was charging on US-made vehicles. China even supposedly agreed to bring its tariffs on USA cars more in line with its duties on automobile imports from other countries. China, meanwhile, will buy an unspecified but "very substantial amount of agricultural, energy, industrial and other products", and expand its purchases of farm products immediately. The tariff is now 40 percent.
"My meeting in Argentina with President Xi of China was an extraordinary one". Farmers, I LOVE YOU!' he tweeted.
The Buenos Aires deal shows that both sides are aware that the tariffs could damage the global economy, it said.
Parag Khanna, founder of the FutureMap consultancy and author of the forthcoming book "The Future is Asian", noted that in speeches to domestic Chinese audiences, Xi is still promoting the economic self-reliance that Made in China 2025 symbolizes.
"The consensus reached by the leaders of our two countries is to halt the imposition of new tariffs and at the same time the two sides' leaders instructed the economics teams of both sides to intensify talks towards the removal of all tariffs that have been imposed", Geng told a daily news briefing.
The 90-day truce in the escalating trade war between the USA and China came during a dinner meeting between the two presidents following the G-20 summit of the world's biggest economies in Buenos Aires. And China's leader will likely expect compromise on complex territorial issues like Taiwan or the South China Sea before the ceasefire will begin to look like a full-fledged peace accord. First off, China and the US have a lot of disagreements, and three months is not a lot of time to solve them - especially since the two countries have been at it for over a year.
The US and China have been embroiled in a trade war this year which has seen the US hit China with tariffs on $250bn (£195.9bn) worth of goods since July, and China retaliate with duties on some $110bn of US goods over the same period.
Speaking to reporters aboard Air Force One on Saturday, Trump said, "It's an incredible deal".
Caterpillar, Ford and other US corporate giants have complained that the higher Trump tariffs, if kept in place, would guarantee higher costs and lower profits. While the U.S. and China have agreed to negotiate, China appears unlikely to fundamentally alter its policies, and it is unclear whether Trump will be satisfied with a deal that falls considerably short of his demands.