"We are making business and operational changes that, along with the foundational changes we've already made, will put us further down the path to become a more profitable, agile and differentiated UPS that is growing in the best parts of the market," Tome said in a statement.
Amazon spokesperson Kelly Nantel told CNBC in a statement that UPS had requested a reduction in volume "due to their operational needs."
"We certainly respect their decision," Nantel said in a statement. "We'll continue to partner with them and many other carriers to serve our customers."