American intelligence agencies are aware that Chinese and Russian spies are listening in on President Trump’s iPhone calls to friends, according to a new report.

The Chinese are using the information to assist them in the ongoing trade dispute between the U.S. and China by figuring out how Trump thinks, what type of arguments he finds persuasive, and who he listens to, the New York Times reports.

White House aides have cautioned Trump against using his iPhone, but he continues to do so.

Already, the Chinese have a list of those Trump often talks to, such as Blackstone Group chief executive Stephen Schwarzman and former Las Vegas casino magnate Steve Wynn. Officials told the Times Beijing wants to use Chinese businessmen and others to pass information to friends of Schwarzman and Wynn that will eventually make its way to Trump through people whose opinion he values.

A spokesperson for Schwarzman told the Times that he “has been happy to serve as an intermediary on certain critical matters between the two countries at the request of both heads of state,” but didn’t comment further. A lawyer for Wynn said Wynn did not have any comment for the Times.

A former official doesn’t believe that Russia is using the information learned on the calls as part of an influence effort like the Chinese. But John Sipher, a veteran of the CIA, said that the Chinese and Russians “would look for any little thing — how easily was he talked out of something, what was the argument that was used.”

U.S. intelligence detected foreign spies were listening to Trump’s calls by intercepting communications between foreign officials, and also from sources in foreign governments.

Trump has a total of three iPhones, one of which functions as a personal phone and hasn’t been modified by the National Security Agency to restrict its vulnerabilities.

Apple declined to comment to the Times.