President Donald Trump has named U.S. Trade Representative Robert Lighthizer to head trade talks with China following a weekend summit with Chinese President Xi Jinping, top White House economic adviser Larry Kudlow said Monday.

The move came after Trump and Xi agreed Saturday to a 90-day cease-fire in their trade war, in which the United States will put off levying additional tariffs and leave the current rate on $200 billion of Chinese goods at 10 percent, rather than implementing a hike on Jan. 1 as previously planned.

Trump tweeted Sunday that China has agreed to reduce and remove tariffs on U.S. cars in the wake of a deal the two countries struck Saturday in Argentina to put off imposing new duties.

China currently imposes a 40 percent tariff on U.S. automobiles. The rate was raised by 25 percentage points in July as part of countermeasures against Washington imposing tariffs on Beijing for alleged theft of intellectual property and technology.

The tweet indicates Beijing made a concession to Washington to try to resolve their trade friction during talks between Trump and Xi on the fringes of the Group of 20 summit in Buenos Aires over the weekend.

"I believe that commitment was made," Kudlow, director of the president's National Economic Council, told reporters on a conference call. "We expect those tariffs to fall to zero."

The United States imposes a 2.5 percent tariff on imported cars but in July put an additional 25 percent tariff on Chinese vehicles as the first sanction against China's alleged infringement of intellectual property rights.

Later that month, China reduced the tariff rate to 15 percent on all imported vehicles while raising it for U.S. cars to 40 percent. Lighthizer, a hard-liner on China, said Wednesday that Washington would consider taking a countermeasure of raising the rate on cars from China from the current 27.5 percent to 40 percent.

Trump agreed with Xi on Saturday that the two countries will talk about technology and intellectual property rights issues within the 90-day period, but if they fail to reach an accord the United States will raise existing 10 percent tariffs to 25 percent on $200 billion of Chinese goods.

Kudlow said Monday the 90-day negotiating period will start on Jan. 1, 2019, but the White House later issued a correction stating that it actually began on Saturday.

Treasury Secretary Steven Mnuchin also said China has made additional trade commitments worth more than $1.2 trillion as part of the Trump-Xi deal.