Trump says your Amazon package should cost more.

An analyst estimates the online retailer paid about $2 per package for delivery in the past

If President Donald Trump has his way, the cost of delivering Amazon packages will go up.

The nation’s chief in a morning tweet Friday once again took aim at the Seattle e-commerce behemoth, this time demanding it pay the U.S. Postal Service “MUCH MORE” for delivering Amazon packages.

“Why is the United States Post Office, which is losing many billions of dollars a year, while charging Amazon and others so little to deliver their packages, making Amazon richer and the Post Office dumber and poorer?” Trump tweeted.

“Should be charging MUCH MORE!”

The tweet before dawn Eastern time appeared to put a hit on Amazon’s stock, with the price falling 1.4 percent Friday to close at $1,169.47.

Amazon has felt the presidential sting before, in statements condemning not only the company but the Washington Post newspaper owned by Amazon CEO Jeff Bezos. In August, Trump tweeted that Amazon was causing “great damage to tax paying retailers,” although the company in April reportedly began directly collecting sales taxes on goods sold. As a presidential candidate, Trump charged that Bezos was using the Post to defend himself from higher taxes, a comment Bezos called inappropriate.

One analyst’s earlier estimate suggests Amazon may in fact be receiving a deep discount when using the U.S. Postal Service as a delivery agent. Bernstein analyst David Vernon said in 2015 that the mail service probably took care of 40 percent of Amazon’s deliveries in 2014, for about $2 a package — about half of what UPS or FedEx would charge, according to Bloomberg.

Amazon is working busily to free itself from the need to use the U.S. Postal Service and other delivery agents to bring packages to consumers, investing heavily in drone-delivery research and development.