Donald Trump has called for the immediate resignation of Intel’s chief executive, Lip-Bu Tan, citing a “highly conflicted” past.

“The CEO of INTEL is highly CONFLICTED and must resign, immediately. There is no other solution to this problem,” Trump wrote on his Truth Social network on Thursday. Trump did not explain the nature of the conflicts.

Tan has extensive experience in the semiconductor industry and venture capital world, including founding venture capital firm Mobius Venture Capital in San Francisco and two companies in Hong Kong that have made hundreds of millions of dollars of investments in Chinese tech companies. He has also served as an early investor in Semiconductor Manufacturing International Corp (SMIC), now China’s largest chipmaker.

Intel declined to comment on Trump’s demand, as did a White House spokesperson. The company’s stock price dropped 3 percent in pre-market trading in New York on Thursday morning after Trump’s post.

Tan, 63, has been a fixture in Silicon Valley for decades, having founded multiple companies and served in leadership roles at others, such as Cadence Design Systems. Last week, Cadence acknowledged it violated U.S. export controls by providing its chip design tools to a Chinese university with military ties.

Tan replaced former Intel CEO Pat Gelsinger, who was ousted by the company’s board in December. The board’s decision came at a challenging time for Intel, the dominant Silicon Valley firm in advanced chips. Intel has fallen behind global leader Taiwan Semiconductor Manufacturing Company (TSMC), based in Taipei, in the latest generation of chip technology and is also missing out on the latest rush to build artificial intelligence (AI) chips.

The U.S. government has provided Intel with billions of dollars in subsidies and loans to try to restore its competitive position. But with TSMC many years ahead in leading-edge chipmaking, the pressure on Tan has been immediate and intense.

Tan made waves in July when he said that Intel may need to stop developing next-generation chipmaking technology without a “significant external customer.” Should Intel back away from next-generation manufacturing, it would cede that market to TSMC, giving the Taiwanese company a de facto monopoly on leading-edge chips, with potential implications for U.S. national security.

Intel has since found a new partner to co-develop future chips, but Tan has also laid out a series of aggressive cost-cutting measures aimed at returning Intel to profitability. While some investors have praised these efforts, they have also added to concerns about the company’s future.

In his letter, Republican Senator Tom Cotton expressed concern over the fact that Intel has received billions of dollars of taxpayer money as subsidies, and must ensure the highest levels of security and integrity. “Intel is required to be a responsible steward of American taxpayer dollars and to comply with applicable security regulations. Mr Tan’s associations raise questions about Intel’s ability to fulfill these obligations,” Cotton wrote.

Tan’s previous work leading up to his appointment, including his time at Cadence and his investments in Chinese firms, has also come under increased scrutiny. Those investments could make Tan a target in Washington. In July, Congress passed an amendment that would bar companies that invest more than 10 percent of their assets in Chinese companies from receiving government subsidies. Intel has yet to comment on how that might affect the company.