The conflict between Amazon and Google is escalating: Google once again started to block access to YouTube on Amazon’s Echo Show device Tuesday, and is notifying users of Amazon’s Fire TV that they won’t be able to access YouTube anymore starting January 1st.

In an unusually frank statement, a Google spokesperson squarely blamed Amazon’s unwillingness to strike a business deal with Google for the step:

​“We’ve been trying to reach agreement with Amazon to give consumers access to each other’s products and services. But Amazon doesn’t carry Google products like Chromecast and Google Home, doesn’t make Prime Video available for Google Cast users, and last month stopped selling some of Nest’s latest products. Given this lack of reciprocity, we are no longer supporting YouTube on Echo Show and FireTV. We hope we can reach an agreement to resolve these issues soon.”

Amazon shot back Tuesday afternoon, sending Variety the following statement:

“Echo Show and Fire TV now display a standard web view of YouTube.com and point customers directly to YouTube’s existing website. Google is setting a disappointing precedent by selectively blocking customer access to an open website. We hope to resolve this with Google as soon as possible.”

This latest development is the escalation of a long-simmering conflict that first bubbled to the surface in September, when Google started to block Amazon’s implementation of YouTube on the Echo Show, the company’s latest voice-enabled speaker with integrated display. At the time, both companies blamed each other for the outage, and Amazon eventually managed to get YouTube working again on the device in November.

However, a source familiar with YouTube’s thinking told Variety Tuesday that this newer implementation also violated YouTube’s terms of service by layering voice control onto a web app that wasn’t designed for voice interaction.

The take-down of YouTube on Fire TV clearly shows that this isn’t just about technical differences. Both companies have long had their differences over Amazon’s implementation of Android, and its decision to run a separate app store for its devices.

The conflict between the two companies significantly escalated in late 2015, when Amazon stopped selling Google’s Chromecast streaming adapter, which previously was the top-selling streaming device on Amazon.com.

Amazon also never sold Google’s Home smart speaker, and the company quietly booted some of Nest’s products, including the nest thermostat E, off its store after Google first blocked YouTube on the Echo Show in September — something that will undoubtedly harm the sales of these devices during the crucial holiday season.

Now, Google may be trying to beat amazon at its own game. YouTube regularly lists as one of the most-watched channels on streaming devices, and not having access to it could have a significant impact on Fire TV sales. Case in point: Sales of the Echo Show declined notably after Google first blocked access to YouTube in September.

Update: 1:45pm: This post was updated with a statement from Amazon.