US officials are warning the EU not to single out American companies with “protectionist” tech policies.

The EU has a much higher standard for consumer protections and privacy, policies that have put it on a collision course with numerous US companies. In addition, some specific EU countries, like Ireland and the Netherlands, have worked out favorable tax deals with US companies. The EU has repeatedly tried to end those deals, although courts have so far ruled in favor of keeping them in place.

US officials are now warning the EU not to go too far in targeting US companies, according to the Financial Times, via Ars Technica. Of particular concern were comments by Andreas Schwab, a member of the European Parliament.

“We are particularly concerned about recent comments by the European Parliament rapporteur for the Digital Markets Act, Andreas Schwab, who suggested the DMA should unquestionably target only the five biggest US firms,” said an email, sent by National Security Council staff to the EU delegation, seen by the Financial Times.

The email continued: “Comments and approaches such as this make regulatory co-operation between the US and Europe extremely difficult and send a message that the [European] Commission is not interested in engaging with the United States in good faith to address these common challenges in a way that serves our shared interests.

“Protectionist measures could disadvantage European citizens and hold back innovation in member-state economies. Such policies will also hinder our ability to work together to harmonize our regulatory systems,” the email said.

US and EU officials have stressed the importance of working together to improve regulation of Big Tech. Not surprisingly, an NSC official told the Financial Times the segments the outlet saw did not reflect the full context. Either way, it’s clear fair scrutiny of American, as well as non-American, companies will likely be a critical negotiating point in any future agreements.