The EU’s powerful anti-trust authority on Wednesday ordered US chipmaker Broadcom to immediately halt uncompetitive sales practices, using an unprecedented weapon against US Big Tech.

The European Commission took the extremely rare move of ordering interim changes from one of Silicon Valley’s pioneer companies while the EU investigation is still underway, citing “irreparable” threats to competition.

The move comes at a delicate time in trans-atlantic relations and risks raising the hackles of US President Donald Trump, who has accused the EU repeatedly of unfairly targeting US giants.

It also falls two days before $7.5 billion worth of European goods are slapped with US tariffs in retaliation for illegal EU subsidies to Airbus, the plane maker.

EU Competition Commissioner Margrethe Vestager warned that Broadcom’s behaviour “is likely, in the absence of intervention, to create serious and irreversible harm to competition”.

“We have strong indications that Broadcom, the world’s leading supplier of chipsets used for TV set-top boxes and modems, is engaging in anticompetitive practices,” she said.

Broadcom in a brief statement said it intended to appeal the decision in the European courts “and in the meantime comply with the commission’s order”.

The ongoing investigation centres on Broadcom’s highly popular TV and modem chipsets, devices that offer television and internet access to customers at home or work.

The commission said it had obtained information that Broadcom might be requiring firms to buy only its components, or granting them rebates and other advantages if they buy in high volume.

The commission said it had also heard Broadcom might be bundling products or deliberately undermining the “interoperability” between Broadcom products and other products.

The commission in June sent a “statement of objections on interim measures” to Broadcom requiring it to swiftly stop such alleged practices and the company now has just 30 days to implement the changes.