The U.S. Treasury proposed barring Americans from investing in Chinese companies that develop any AI system.

Under the current rule, Americans can’t invest in the most powerful Chinese AI models, but they can still fund smaller AI projects if they report the deal to Treasury.

The new proposal would ban all of those AI investments, and it would also add high-bandwidth memory, photonic chips and radiation-hardened chips to the chip types Americans can’t invest in.

The proposal would also ban investments in two new areas: hypersonic weapons and biotech, including brain-computer interfaces and automated lab software.

Today the rule covers only China, but the proposal adds Russia, Iran, North Korea and Cuba.

Buying public stocks, index funds or small fund stakes up to $2M would stay allowed, so the rule mainly hits venture and private equity deals.

Treasury won’t publish a list of banned companies, so investors must check each deal themselves or risk fines and being forced to sell.