Trump uses the phones to speak to “old friends,” and domestic spy agencies have determined China is seeking to use information from the calls to keep a trade war with the US from escalating, the paper said, citing unidentified current and former US officials.

The agencies are said to have learnt of the eavesdropping from people inside foreign governments and through intercepting communications between foreign officials, the report said.

The Chinese have pieced together a list of people whom Trump regularly speaks to in hopes of using them to influence the president, according to the report.

Russia’s operation is believed to be less sophisticated because of his “apparent affinity” for President Vladimir Putin, a former official is cited as saying.

While Trump is using his secure landlines more often, aides are said to be frustrated that he has refused to give up his two official iPhones and a personal one.

The official devices have been modified by the National Security Agency to limit their capabilities, but the personal phone where he can store contacts isn’t, the paper said.

None are completely secure as calls can be intercepted as they travel through cell towers, cables and switches that make up national and global phone networks, the report said.

Blackstone Group chief executive Stephen Schwarzman and Las Vegas casino magnate Steve Wynn are among “ideal targets” identified by China who can eventually convey the Asian nation’s views to Trump, the New York Times said.

A representative for Wynn declined to comment while a spokeswoman for Schwarzman said 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.” Apple declined to comment to the paper on Trump’s iPhones.