Shares of U.S. chipmakers fell in premarket trading Wednesday following a report that the Biden administration is planning new curbs on export of computing chips for artificial intelligence to China as early as July.

Companies that rely on the world's second largest economy for at least a fifth of their revenue such as Nvidia, Advanced Micro Devices and Intel fell as they get trapped in the U.S.-China crossfire.

Nvidia fell 4%, Advanced Micro Devices 3.3% and Intel 0.7%, while futures tracking the tech-heavy Nasdaq 100 index edged 0.5% lower.

The new restrictions being considered by the Commerce Department would include a ban on the sale of Nvidia's advanced chip called A800 without a special U.S. export license.

"With an update on export controls now expected, investors will assess just how limiting the new rules will be for chip makers' sales," said Susannah Streeter, head of money and markets, Hargreaves Lansdown.

"A handful of tech companies pack a huge punch on Wall Street due to their sheer size, so any wobble in confidence reverberates on indices."

Rising expectations over the advancements in AI has helped Wall Street gains this year, with Nvidia at the pole position on the S&P 500 index with its 187% jump so far this year.

But the sharp rise in shares have also sparked doubts over lofty valuations.

Nvidia is trading at 47 times its expected 12-months earnings, while AMD is at a 31.2 multiple and Intel at 31.8, way above the S&P 500's multiple at 19, according to Refinitiv data.

The Philadelphia chip index has surged more than 44% so far this year, far ahead of the benchmark index's 14% rise.

Among other chip stocks, Marvell Technology, Applied Materials, Intel, Microchip Technology fell between 1.1% and 3% on Wednesday.

Across the Atlantic, Nordic Semiconductor, Dutch chipmaker ASML, Milan-listed STMicroelectronics , however, gained between 1.2% and 2%.