EXCLUSIVE-U.S. willing to talk trade with China, no session set yet -official

WASHINGTON, April 5 (Reuters) - The United States is willing to negotiate with China on trade, but only if talks are serious, as previous attempts produced little progress, a senior U.S. official told Reuters late on Thursday as trade tensions between the two nations escalated.

No formal negotiating sessions have been set, the official said. "There is ongoing communications with the Chinese on trade," said the official, who requested anonymity to discuss the Trump administration's trade strategy.

The official said Republican President Donald Trump, who has already sought $50 billion in new tariffs on China, will insist on "verifiable, enforceable and measurable deliverables" from China in any trade negotiations. (Reporting by Steve Holland; Editing by Kevin Drawbaugh and Peter Cooney)