An influential Republican lawmaker has urged the US Commerce Department to halt all technology exports to Huawei and China's top semiconductor firm following the discovery of new chips in Huawei phones that he said may violate trade restrictions.

The comments from Mike Gallagher, the chair of the House of Representatives' committee on China, come after Chinese electronics giant Huawei last week started selling a phone called the Mate 60 Pro.

The phone contains a chip that analysts believe was made with a technology breakthrough by Semiconductor International Manufacturing Corp (SMIC).

"This chip likely could not be produced without US technology and thus SMIC may have violated the Department of Commerce’s Foreign Direct Product Rule," Gallagher said in a statement.

"The time has come to end all US technology exports to both Huawei and SMIC to make clear any firm that flouts US law and undermines our national security will be cut off from our technology."

On Tuesday, US national security adviser Jake Sullivan said the US needed to get “more information” on the precise “character and composition” of the chip in the new Huawei phone.

The firm had released its Mate 60 Pro smartphone last week during US Commerce Secretary Gina Raimondo's visit in China.

The Mate 60 Pro is powered by its proprietary chip Kirin 9000s and manufactured by SMIC using an advanced seven nanometre (nm) technology, according to a teardown by Ottawa-headquartered TechInsights.

Its findings and claims by early users about the phone's powerful performance indicate China is making some headway into developing high-end chips, even as Washington has over the recent years ramped up sanctions to cut its access to advanced chipmaking tools.

It "demonstrates the technical progress China’s semiconductor industry has been able to make without EUV tools. The difficulty of this achievement also shows the resilience of the country’s chip technological ability," TechInsights analyst Dan Hutcheson said.

EUV refers to extreme ultraviolet lithography and is used to make seven nm or more advanced chips.

The most advanced chip SMIC had previously been known for making was 14nm, as it was barred by Washington in late 2020 from obtaining an EUV machine from Dutch firm ASML.

"At the same time, it is a great geopolitical challenge to the countries who have sought to restrict its access to critical manufacturing technologies. The result may likely be even greater restrictions than what exist today", Hutcheson warned.

Huawei was placed on a US trade blacklist in May 2019 over national security concerns, forcing its US suppliers and others to obtain a special licence to ship goods to it.

SMIC was added to the so-called entity list in December 2020, over US concerns that it could divert advanced technology to military users.

The trade restrictions imposed on Huawei and SMIC include the Foreign Direct Product Rule meant to bar any company anywhere in the world from using tools from the United States to manufacture a chip for Huawei. (Reuters, RTHK)