(Reuters) -Perplexity AI said on Tuesday it has received a legal threat from Amazon.com ( AMZN ) demanding that the startup block the AI agent on its Comet browser from shopping on the e-commerce giant's platform on a user's behalf.

The startup, which has grown rapidly amid the boom in AI assistants, rejected Amazon's ( AMZN ) claims, saying it was using its market dominance to stifle competition.

Perplexity called the move a broader threat to user choice and the future of AI assistants. "Bullying is when large corporations use legal threats and intimidation to block innovation and make life worse for people," the company wrote in a blog post.

Amazon ( AMZN ) said it has repeatedly requested that Perplexity remove the online retailer from the Comet experience, "particularly in light of the significantly degraded shopping and customer service experience it provides".

Third-party apps making purchases for users should operate openly and respect businesses' decisions on whether to participate, Amazon ( AMZN ) said in a statement.

The clash between Amazon.com ( AMZN ) and Perplexity highlights an emerging debate over how to regulate the growing use of AI agents and how they interact with websites. 

Perplexity is among many AI startups seeking to reinvent the web browser around artificial intelligence, aiming to make it more autonomous and capable of handling everyday online activities, from drafting emails to completing purchases.

Amazon ( AMZN ) itself is developing similar tools, including "Buy For Me", a feature allowing users to shop across brands within its app, and "Rufus", an AI assistant that can recommend products and manage carts.

The AI agent on Perplexity's Comet browser acts as an assistant that can make purchases and comparisons on behalf of users. The company said user credentials remain stored locally and never on its servers. "Easier shopping means more transactions and happier customers. But Amazon ( AMZN ) doesn't care, they're more interested in serving you ads," the company said.

The startup argued that users have the right to choose their own AI assistants, portraying Amazon's ( AMZN ) move as an attempt to safeguard its ad-driven business model.