The Trump administration is seeking to join Elon Musk’s appeal against a €120mn EU fine imposed on his social media platform X, escalating the transatlantic clash over Brussels’ efforts to rein in US tech companies.

The US Department of Justice filed an application to intervene in cases brought by Musk and X seeking annulment of the penalty at the EU’s General Court in Luxembourg. Assistant attorney general Brett Shumate said the European Commission had attempted to expand its regulatory authority to reach American companies outside its jurisdiction.

The European Commission fined X in December last year under the Digital Services Act, citing breaches involving transparency, data access and the design of its blue-tick system. The DOJ argued that the Commission improperly scrutinised Musk personally and calculated the fine using revenue from other companies he controls rather than X’s EU earnings.

The DSA has become a flashpoint between Brussels and US tech companies, with Donald Trump’s administration and vice-president JD Vance criticising the penalty. X has separately faced EU scrutiny over risks linked to its AI chatbot Grok. Apple is also appealing a €500mn fine under the Digital Markets Act.