An acquisition of Arm by Nvidia looked in doubt as the US-based chipmaker does not expect the $40 billion deal for the SoftBank Group-owned design business to be approved by regulators, Bloomberg reported.

Nvidia is the most valuable US chipmaker by market capitalisation and is considering dropping the takeover bid due to a lack of progress with regulators, Bloomberg stated.

Sources told the news service Nvidia and SoftBank continue to push for support and are committed to a deal, with no final decision made.

However, SoftBank is reportedly again looking at an Arm IPO as an alternative.

Richard Windsor, founder of research blog Radio Free Mobile, wrote an IPO would a better outcome for the industry, returning Arm to public ownership, which he believes is the simplest solution.

But scuppering the transaction would be worse for SoftBank, which “may have to accept a far lower return on investment by being forced” to list the unit.

The proposed deal hit regulatory challenges because of the wide range of companies using Arm designs.

Bloomberg reported likely resistence in China even if other regulators approve the deal.