Google boss Eric Schmidt said Monday his company's biggest competition as a search engine came from e-commerce giant Amazon, not from its traditional rivals.

In remarks prepared for delivery in Berlin, Schmidt hit back at accusations that Google as the world's biggest search engine enjoyed unchallenged market dominance, saying that the sector was targeting the company on several fronts.

"Many people think our main competition is Bing or Yahoo. But, really, our biggest search competitor is Amazon," he said.

"People don't think of Amazon as search, but if you are looking for something to buy, you are more often than not looking for it on Amazon."

He said that while Amazon's main mission was "the commerce side of the equation", the company was essentially "answering users' questions and searches, just as we are".

He added that Google's outsize market position was under constant threat from upstarts and innovators.

"Someone, somewhere in a garage is gunning for us. I know, because not long ago we were in that garage," he said.

"Change comes from where you least expect it. The next Google won't do what Google does, just as Google didn't do what AOL did."

He said those who accused Google of gaining monopolistic power didn't understand the sector.

"The reality is that Google works very differently from other companies that have been called gatekeepers, and regulated as such. We aren't a ferry. We aren't a railroad," he said.

"We aren't a telecommunications network or an electricity grid, with only one line going to your home, and no competitors allowed. No one is stuck using Google."

Google has been locked in battle with EU regulators who say it will face formal charges if it fails to improve its proposals to resolve anti-trust complaints over its search engine.

The California-based company previously avoided potentially billions in fines when it struck a deal in February with the European Commission.

It agreed at the time to give equal prominence to rival services in its search results after competitors -- including Microsoft and TripAdvisor -- argued the company has abused its dominant position in the European market, where it accounts for 90 percent of traffic.

But the deal collapsed when the Commission received a flurry of new complaints.