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

The nation’s chief in a morning tweet Dec. 29 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.

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“Should be charging MUCH MORE!”

The tweet before dawn Eastern time appeared to put a hit on Amazon’s stock, with the price opening almost 1 percent lower and continuing to slide somewhat to $1,178.82 by 8:30 a.m. after opening at $1,182.35.

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.

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.

Photo: Packages travel down a conveyor belt before being scanned and a shipping address is attached at the Amazon fulfillment center in Tracy, Calif., on Tuesday, April 12, 2016. (Doug Duran/Bay Area News Group)

Tags: amazon, bezos, delivery, Donald Trump, FedEx, Jeff Bezos, package, president, Trump, U.S. Postal Service, UPS, washington post