Tesla and SpaceX CEO Elon Musk said that if President Donald Trump follows through on pulling the US out of the Paris climate-change agreement, he would "have no choice" but to stop advising the White House, the media reported.
Musk's line in the sand is the latest sign of tension between Silicon Valley and Trump just as his administration attempts to attract tech executives to the White House for a sweeping, high-profile summit on June 19, Politico news reported.
"Don't know which way Paris will go, but I've done all I can to advise directly to POTUS (President of the US), through others in the White House and via councils, that we remain," Musk tweeted on Wednesday.
Musk followed up with a tweet saying, "Will have no choice but to depart councils" if Trump pulls out of the Paris deal backed by nearly 200 other countries.
Trump is expected to withdraw the US from the climate agreement on Thursday.
Other major tech companies, including Apple, Facebook, Google and Salesforce, have put their names to a full-page ad that will run on Thursday in the New York Times and the Wall Street Journal, calling on Trump to "advance US interests by remaining a full partner in this vital global effort".
The ad ran earlier this month but has been renewed because of the news of Trump's thinking on the Paris deal, reports Politico.
Musk's warning carries particular weight because he's become one of the Trump White House's go-to tech industry executives. He has taken part in the so-called President's Strategic and Policy Forum.
Uber CEO Travis Kalanick stepped down from that group in February after a public backlash.
At the time, Musk decided to stay involved, saying, "I believe at this time that engaging on critical issues will on balance serve the greater good."