CNBC's Jim Cramer is warning against trading stocks on the roller coaster of U.S.-China headlines as the two countries restarted high-level talks aimed at ending their 15-month-old trade war on Thursday.

Markets are "hostage to events that are not only totally out of our hands, but I think totally out of the president's hands," Cramer said on "Squawk on the Street."

"I am describing an unfathomable market," he declared, "where if you have conviction, you are out of your mind," meaning fundamental cases for buying or selling are useless.

In the flip-flopping between trade talk pessimism and optimism, the latter was winning on Wall Street in midday trading. The Dow Jones Industrial Average was more than 200 points higher.

Stocks surged higher after President Donald Trump said he will meet Friday with Chinese Vice Premier Liu He, leader of the Chinese trade delegation in Washington for the latest round of talks Thursday and Friday.

Overnight, Dow futures plunged more than 300 points on a report that the trade talks might end earlier than expected. However, the White House later denied those claims, which helped futures recover.

Later confusion ensued after Bloomberg reported the U.S. might suspend next week's tariff increase in exchange for a currency pact. The New York Times also reported the Trump administration was looking to allow the sale of some supplies to China's Huawei, months after the administration restricted sales to the telecom giant over concerns of national security.

Stocks were on an unsure path in early Thursday trading on Wall Street until Trump tweeted about Friday's Liu meeting.

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However, Cramer suggested there's still plenty of time left in the trade war for headlines to send stocks plunging again, saying that "it is just impossible."

Cramer pointed to the whiplash of confusion around Apple, which has been threatened by the two countries' increasing, retaliatory measures on one another.

"You sell Apple on the news that the trade talks are going badly," the "Mad Money" host said. But then Apple shares move higher, after the company gained favor with China by removing an app that antigovernment protesters in Hong Kong were using to track police.

"Do you buy Apple off that?" he asked. "You upgrade Apple because Apple is doing better with the [new iPhones]," he said, then questioned what would happen "if the trade talks go badly."