Nvidia admitted that the US Federal Trade Commission has "expressed concerns" over its proposed acquisition of chip designer Arm.
The regulator is investigating the deal, which is also being scrutinized by the UK, EU, and China.
"Regulators at the US FTC have expressed concerns regarding the transaction when we are engaged in discussions with them regarding remedies to address those concerns," chief financial officer Colette Kress said in the company's latest earnings call.
"The transaction has been under review by China's antitrust authority, pending to formal case initiation... In the UK, they have also voiced national security concerns. We have begun the phase 2 process in the EU and UK jurisdiction.
"Despite these concerns and those raised by some Arm, licensees, we continue to believe in the merits and the benefits of the acquisition to all -- of the acquisition to Arm, to its licensees, and the industry."
In its first phase of investigation, the UK's Competition & Markets Authority said that it "does not believe any form of behavioral remedy would address the competition concerns identified."
Nvidia first proposed acquiring Arm for $40bn back in September 2020, but that price has increased due to Nvidia's share price surging over the past year. Should the deal fall apart, Arm and current owner SoftBank could raise money by going public.