The US State Department announced Tuesday it would deny visas to Breton and four activists, accusing them of seeking to "coerce" American social media platforms into censoring viewpoints they oppose.

"We have requested clarifications from the US authorities and remain engaged. If needed, we will respond swiftly and decisively to defend our regulatory autonomy against unjustified measures," said a statement from the Commission.

"Our digital rules ensure a safe, fair, and level playing field for all companies, applied fairly and without discrimination."

The statement also said: "Freedom of expression is a fundamental right in Europe and a shared core value with the United States across the democratic world.

"The EU is an open, rules-based single market, with the sovereign right to regulate economic activity in line with our democratic values and international commitments," the Commission said.