When billions of dollars in new US tariffs against China come into effect on Friday, just $250 million worth of chips will be hit.

But the levies have triggered deeper anxieties among US semiconductor companies about disruption to their close trade links with China — as well as worries that Washington is shooting at the wrong target in trying to protect a key part of the American technology industry.

A reminder of the high stakes came on Tuesday, as news spread of a preliminary injunction from a Chinese court banning some sales in China by Idaho-based Micron Technology, whose memory chips are used in many smartphones, computers and other devices.

Fears that the company would be at least partially shut out of a market that accounted for about half its revenues last year sent Micron’s shares down more than 5 per cent on Tuesday.

To many observers in the US, the timing of the Chinese ruling, which came in a patent case, was no coincidence. Ambrish Srivastava, an analyst at BMO Capital, said it appeared to be a “tit-for-tat” move with tariffs inked. “It’s showing how much leverage China has,” he said.