Donald Trump has called on the new chief executive of Intel, Lip-Bu Tan, to step down from his position.

The former president, in a post published Thursday on Truth Social, wrote, “The CEO of INTEL is highly CONFLICTED and must resign, immediately. There is no other solution to this problem.”

The post, published on Trump’s Truth Social platform, did not explain what exactly Tan’s conflicts were. It did not respond to a request for comment.

The statement comes shortly after Republican Senator Tom Cotton sent a letter to the chipmaker’s board chair, Frank Yeary, warning that Tan’s “business interests in China and his decades-long pattern of investing in Chinese technology companies raise concerns about the security and integrity of Intel’s operations.”

In the letter, Cotton, who has long pushed the Biden administration to take a harder line with China, also raised the issue of Tan’s investment history with Semiconductor Manufacturing International Corp (SMIC) and accused him of building “a decades-long personal investment portfolio in Chinese tech companies, one that includes SMIC, China’s largest chip manufacturer.”

Tan, a Silicon Valley fixture and veteran semiconductor investor, leads a San Francisco-based venture capital firm and Hong Kong-based holding company, which over the years has invested in a range of Chinese tech companies.

Tan’s past investments in China are just one part of the scrutiny he has come under. Earlier this year, Tan was CEO of Cadence Design Systems, a California-based software firm that helps design chips. Last week, Cadence admitted that it had violated U.S. export control laws after it sold its chip design software to a Chinese university, which the company only later learned had military ties.

The controversy over Cadence, for which Tan left in February, has added to criticisms that Tan’s extensive business and investment history in China is a potential conflict that could complicate Intel’s ability to lead the U.S. as its largest advanced chipmaker.

Intel did not respond to a request for comment, and the White House declined to comment on Trump’s statements. Tan’s arrival in March as Intel’s CEO had already come at a critical time for the Silicon Valley giant. Intel has been trying to play catch-up with Taiwan Semiconductor Manufacturing Company (TSMC), a manufacturer of cutting-edge chips that supply the world’s largest tech companies.

Intel has also emerged as a key part of the U.S. national security response to China’s rise as a chipmaking power. Intel’s California factories are the only U.S.-based chipmakers with advanced manufacturing capacity. Intel is also the only U.S.-based company that’s able to produce leading-edge chips, although it has lost out in a major way to TSMC and its Taiwan counterparts in a new boom area for semiconductors: artificial intelligence chips.

Washington has stepped in to back Intel with billions in subsidies and loans in recent years as part of a wider drive to bolster domestic semiconductor manufacturing capacity. In Intel’s case, the funds will support two new factories in Arizona. The White House declined to comment on Trump’s statement.

Intel declined to comment. But the controversy was reflected in the company’s stock price, which was trading 3 percent down in pre-market in New York on Thursday morning, shortly after Trump’s post.

Tan replaced Pat Gelsinger as CEO in March, after the company’s board ousted the long-time CEO in December. Tan, who had been with Intel for a decade, will take on the dual challenges of streamlining Intel’s cost base to restore profitability while also battling TSMC in leading-edge manufacturing.

In July, Tan, in his first public comments on the situation, said the company needs to find a “significant external customer” to back its next-generation manufacturing technology, or Intel will be forced to cease further development.

Intel is at a key inflection point in the global chip wars

For Intel and Tan, the stakes of the manufacturing race are high. If Intel were to cede the latest generation of manufacturing technology to TSMC, the Taiwanese company would essentially hold a monopoly on leading-edge chips, and the U.S. semiconductor industry and national security could suffer.

Tan, on top of the challenges with costs and TSMC, has also announced a round of cuts and asset sales. The job cuts have won support from some analysts and investors, who argue that Intel needs to slim down. But it has also added to the sense of uncertainty among Intel’s shareholders about the company’s direction.

Senator Cotton, in his letter to Intel’s board, urged the company to take a close look at Tan’s history with Chinese companies. “Intel is required to be a responsible steward of American taxpayer dollars and to comply with applicable security regulations,” Cotton said in the letter. “Mr Tan’s associations raise questions about Intel’s ability to fulfill these obligations.”