The remarks helped deepen losses on Wall Street, which opened lower on Thursday following downbeat economic forecasts for major European economies.
President Donald Trump last week said he expected to meet with China's President Xi Jinping in person "in the near future" to seal a final trade deal.
But top White House economist Larry Kudlow told Fox Business on Thursday that "No date has been set, no time, no place, no nothing at the moment."
And while Trump was "optimistic" about prospects for a deal, there remains a "sizeable distance" separating the two sides, Kudlow said.
The benchmark Dow Jones Industrial Average lost more than 300 points following Kudlow's remarks and shortly before 1730 GMT was down 1.3 percent for the day at 25,075.31.
Last week, Trump and Chinese officials had expressed optimism during the second round of talks in Washington about chances of striking a bargain but they released few details about progress in their talks.
The two sides have three weeks before US duty rates on many Chinese goods are due to jump sharply, which economists say could further weaken the global economy.
CNBC also reported Thursday that an unnamed senior administration official said it was "highly unlikely" a Trump-Xi meeting could occur before the March 1 tariffs deadline but could happen "shortly thereafter."