Brian Nelson, the department’s under-secretary for terrorism and financial intelligence, also said that the sanctions were still in place.

He said they were aimed at “encouraging behaviour change”, and that once the department saw such change, the companies involved would be struck off the list.

Nelson said sanctions would see money in US accounts or accounts with a US correspondent blocked or frozen, thereby preventing these companies from accessing funds.

“And it’s very disruptive to your ability to do business that is cross-border because it is very, very difficult to avoid a touch point with the US financial system,” he said in an interview with several media outlets.

Nelson said that sanctions were a powerful tool, and that the department had found them effective in the context of disrupting activities meant to drive profit or provide capital.

“From that perspective, we think, of course, that they are impactful.

“But I think the more impactful thing at the end of the day is the partnership with jurisdictions and the capacity to make anti-money laundering and countering the financing of terrorism ‘regimes’ more resilient.”

The US Treasury imposed sanctions on the four Malaysia-based companies in December.

It was reported that these companies were providing components for Iran’s weapons programme.

Washington recently imposed further sanctions targeting Iran, including over Iranian drones used by Russia in the war in Ukraine, as the US seeks to increase pressure on Tehran after its attack on Israel.

Nelson is in Malaysia to advance the Treasury’s work in countering terrorist financing and revenue generation for Iran and its proxies.

Reuters previously reported that there had been an uptick in money moving to Iran and its proxies, including Hamas, through the Malaysian financial system.

He is also in the country to discuss ways to disrupt Russia’s ability to sustain its war in Ukraine.