US President Donald Trump has stopped HieFo Corp's US$3 million purchase of assets from New Jersey aerospace and defence firm Emcore, citing national security concerns tied to China, reported Reuters.

In a White House order, Trump said HieFo was controlled by a Chinese citizen and that its 2024 acquisition of Emcore's businesses could impair US national security.

The Committee on Foreign Investment in the United States flagged a security risk during its review, the Treasury Department said, though it did not specify the nature of the threat.

Emcore, which was publicly traded at the time and later taken private, said HieFo acquired its chips unit and indium-phosphide wafer fabrication operations for $2.92 million.