It would be “impossible” to move 40% of Taiwan’s semiconductor capacity to the U.S., the island’s top tariff negotiator said, pushing back against recent comments by American officials who called for a major production shift.

In an interview with Taiwanese television channel CTS that was broadcast late on Sunday, Taiwan Vice Premier Cheng Li-chiun said she had made it clear to Washington that Taiwan’s semiconductor ecosystem, built up over decades, could not be relocated.

“I have made it very clear to the United States that this is impossible,” she said, referring to the 40% goal the U.S. has floated.

That ecosystem will continue to grow in Taiwan, Cheng said, adding that the semiconductor industry would keep investing at home.