WASHINGTON  – President Donald Trump has personally pushed the postmaster general to double the rates the U.S. Postal Service charges Amazon.com and other companies to ship packages, the Washington Post reported on Friday, citing three unnamed sources.

Postmaster General Megan Brennan resisted Trump’s suggestion in private conversations in 2017 and 2018, telling him that package delivery rates are set by contract and reviewed by an independent commission, the sources said, according to the newspaper.

She also told Trump, using a set of slides that showed other companies besides Amazon that partner for deliveries, that the arrangements have helped the financially challenged Postal Service, the Post said, citing the sources.

Trump has repeatedly said without evidence that deliveries for Amazon were costing the service money.

The White House did not immediately respond to a request for comment. Amazon and the Postal Service declined to comment.

Trump has criticized both Amazon and Jeff Bezos, the founder and chief executive officer of the online retailer. Bezos also privately owns The Washington Post, which has published stories that have angered the president.

Trump has repeatedly said without evidence that deliveries for Amazon were costing the service money. Last month, he ordered the creation of a task force to study the Postal Service and its financial difficulties.

Big increases in its parcel delivery rates could cost Amazon and other businesses billions, leading to higher prices for consumers.