Media magnate Rupert Murdoch, whose sprawling corporate empire includes Fox News and the Wall Street Journal, is calling on former New York Mayor Michael Bloomberg to join the race for the White House.

In a message Sunday night on social media, Murdoch endorsed Bloomberg, an independent, as the "greatest mayor."

"With [Republican presidential candidate Donald] Trump becoming very serious candidate, it's time for next billionaire candidate, Mike Bloomberg to step into ring," Murdoch said on Twitter. "Greatest mayor."

In subsequent tweets, Murdoch suggested that he did not agree with some of Bloomberg's "nanny state" positions (like regulations on food serving sizes) but that he is "still a great philanthropic executive."

"I did not say I would vote for him!" Murdoch wrote. "Just a friend I admire."

Murdoch's political opinions are known to tilt conservative but, like Bloomberg's, are more pragmatic than strictly partisan.

Murdoch has made many declarations about the 2016 presidential race in recent weeks, including saying that Trump's hardline positions on immigration were "embarrassing." Murdoch has since called Trump a "friend" and said he is a significant factor in the GOP primary.

Bloomberg has a history as both a registered Democrat and Republican before he switched to an Independent. He served three terms as New York mayor and left office in 2013. He is currently the CEO of his financial news company Bloomberg L.P.