By Alexandra Alper and Karen Freifeld

WASHINGTON (Reuters) -China's top chipmaker SMIC, under sanctions by the U.S., may have violated U.S. export regulations by producing a chip to power Huawei's Mate 60 Pro phone, a senior Commerce Department official said during a congressional hearing on Thursday.

When asked by Congressman Michael McCaul if SMIC broke U.S. export rules to produce the sophisticated chip, Alan Estevez, who oversees export policy, said "potentially yes. We will have to assess."

Pressure has been growing on the Biden administration to take action against SMIC and sanctioned Chinese telecoms firm Huawei since August, when Huawei unveiled a new phone powered by a sophisticated chip manufactured at SMIC.

The Huawei Mate 60 Pro was seen as a symbol of China's technological resurgence despite Washington's ongoing efforts to cripple its capacity to produce advanced semiconductors.

The phone also prompted a review by the Biden administration to learn the details behind the chip that powers it, the most advanced semiconductor China has so far produced.

When asked about SMIC's ability to produce the chip for Huawei using American tools, Estevez said, "I can't talk about any investigations that may or may not be going. But we certain share those concerns."

(Additional Reporting by Michael Martina; Editing by Bill Berkrot)