US President Donald Trump has blocked a planned takeover of chipmaker Qualcomm by Singapore-based rival Broadcom on grounds of national security.
His order cited “credible evidence” that the proposed $140bn (£100bn) takeover “threatens to impair the national security of the US”.
Qualcomm was already trying to fend off Broadcom’s bid.
Broadcom said it strongly disagreed that its proposed takeover gave any cause for concern.
The deal would have created the world’s third-largest maker of microchips, behind Intel and Samsung.