Amazon sells a wide variety of products, but you can't buy anything and everything through the online retailer. The company is reportedly trying to change this by sacrificing huge profits in favor of efficiency—according to a CNBC report, Amazon contacted thousands of third-party retailers via e-mail about taking part in a new program in which Amazon would buy their inventory at full price. Amazon would then be able to sell those products on its website, allowing it to quickly fulfill more orders around the world.

According to the e-mail obtained by CNBC, Amazon is offering "no additional fees" for a limited time for the third-party retailers that choose to be part of the new program. Amazon will buy their inventory at local market price, meaning Amazon likely won't make much of a profit on those items if and when they sell on its website. But according to an Amazon spokesperson that confirmed the authenticity of the e-mail, profit isn't the biggest goal of this program.

"When items are unavailable in a particular geography, we provide customers with selection from another marketplace," the spokesperson said. "This offers customers a wider selection of great brands and helps sellers increase sales."

The program is part of Fulfillment by Amazon (FBA), in which third-party merchants pay a fee for their inventory to be stored and shipped by Amazon. The FBA program is growing fast—in 2016, the number of FBA merchants increased by more than 70 percent. This isn't the first time Amazon has tried out this system, either; the company rolled out a similar program in Europe recently.

FBA makes a lot of sense for retailers of all sizes because they can take advantage of Amazon's well-oiled distribution and shipping machine. It's also positive for Amazon because it gives the company access to more products and allows it to move and ship items faster and more efficiently. Even if Amazon doesn't make a ton of money from sales coming from this program, easier shipping processes lead to faster shipping and delivery schedules, which keep customers happy and shopping on Amazon.

But companies taking part in the new FBA initiative might run into problems with original manufacturers that have declined to sell through Amazon. Birkenstock stopped selling directly through Amazon due to the presence of numerous counterfeit items and unauthorized distributers on the website. Birkenstock doesn't allow authorized retailers to sell through Amazon, either, although it does allow some partners to sell on Amazon. Third-party retailers will have to closely review their relationships with manufacturers before agreeing to sell on Amazon in this new program, lest they face possible legal action.

"If Amazon is in fact soliciting our accounts in order to acquire our products so that they may resell those goods, that causes a serious breach in our agreement with our existing retail partners," Birkenstock USA CEO David Kahan told CNBC. "If indeed this is the case, we will take immediate action with any account that violates our agreement."

Update, 6:25pm: An Amazon representative reached out to Ars with more details about the program, specifically how it defines "inventory" in the new initiative.