Donald Trump’s top economic adviser said the White House doesn’t yet have a deal with China to reduce tariffs on U.S.-made cars, backtracking from a tweet by the president just two days earlier.

“I think it’s coming, OK,” adviser Larry Kudlow said on Fox News Tuesday. “It hasn’t been signed and sealed and delivered yet.”

Trump jolted car stocks by announcing late Sunday that a deal had been reached, following his dinner with Chinese President Xi Jinping on Saturday at the Group of 20 summit in Buenos Aires.

Officials in Beijing declined to comment on the tweet and haven’t confirmed such an agreement. Kudlow told reporters at the White House that he believes the president expects China will reduce its car tariffs to zero.

Trump tweeted on Tuesday that trade negotiations with China have “already started.”