BRUSSELS, June 25 (Reuters) - Amazon AMZN.O and Microsoft's MSFT.O cloud computing services should be designated gatekeepers under EU rules aimed at reining in the power of Big Tech, EU antitrust regulators said on Thursday.

Amazon Web Services and Microsoft Azure, the two largest cloud providers globally, should be designated gatekeepers under the Digital Markets Act which sets out a list of dos and don'ts to ensure a level playing field, the European Commission said.

The preliminary findings by the EU competition enforcer came after a seven-month long investigation.

Amazon said the preliminary assessment disregard the breadth of cloud services available to European customers and risk deterring European investment and innovation.

Microsoft pointed to its rival Google's growing power.

"We remain concerned that ignoring the growing power of Google Cloud and Gemini will tilt the market in a harmful way," a Microsoft spokesperson said.