It’s no secret that Donald Trump has little love for Jeff Bezos, but a report from Axios claims this animosity goes beyond mere dislike. The president is said to be “obsessed with Amazon,” who he believes has gotten unfair tax benefits and preferential treatment from the US Postal Service.

Trump has in the past been vocal about his disdain for Amazon, Bezos, and the Washington Post, which Bezos owns. He called the tech giant a “no-tax monopoly” last year, adding that it was doing great damage to other retailers. The president also said that the US Postal Service was undercharging Amazon, thereby making it “dumber and poorer.”

Trump has repeatedly attacked the Washington Post, too, calling it “Fake News Washington Post,” and a “tax shelter” for Amazon. He famously claimed that Bezos and his firms would “have such problems” if he won the US election.

Update (3/31): During the weekend Trump resumed his attacks on Amazon, saying the company is scamming the US Postal Service. However reports do not seem to support the President's statement. The Postal Regulatory Commission, which oversees the industry, indicates USPS actually benefits from serving Amazon's deliveries, making a profit on them, and that Amazon does not receive special treatment beyond paying a lower rate as other bulk customer would.

According to Axios, Trump wants to change Amazon’s tax treatment over fears that mom-and-pop retailers could be put out of business. One of Axios’ sources who has spoken to the president said: “He’s wondered aloud if there may be any way to go after Amazon with antitrust or competition law.”

Despite Trump’s dislike for the company already being public knowledge, Amazon’s shares fell 7 percent on the back of the report, wiping around $53 billion off its market cap. This comes at a time when tech stocks, especially Facebook’s, are in decline, which could have contributed to Amazon’s slump.

Although Facebook’s Cambridge Analytica scandal has made most of the headlines recently, and despite Mark Zuckerberg agreeing to testify before Congress, Axios says Trump isn’t interested in how the platform handles user data. He also believes the Russia story is a hoax.

Since the report was published, White House Press Secretary Sarah Huckabee Sanders has said the Trump administration isn’t considering any policy changes directed at Amazon. “The president has said many times before he’s always looking to create a level playing field for all businesses and this is no different and he’s going to always look at different ways, but there aren’t any specific policies on the table at this time,” Sanders added.