The US is planning a new assault on China as trade tensions between the two countries heat up.

New proposals would essentially block firms with 25% or more Chinese ownership from buying US companies involved in an "industrially significant technology."

The plans, first reported by The Wall Street Journal, come at a time of escalating trade conflict between the US and China.

A new measure set to be implemented by the US Treasury Department could deepen the growing gulf between the US and China when it comes to their trade relationship.

According to a Wall Street Journal report on Sunday, the Treasury is planning to introduce new curbs on the Chinese ownership of US technology firms, which would effectively amount to a ban on Chinese firms buying up American ones.

If implemented, the new proposals would essentially block firms with 25% or more Chinese ownership from buying US companies involved in what The Journal says is described as "industrially significant technology." The ultimate cutoff point for ownership has not been decided and could be higher or lower, The Journal said.

"The president has made clear his desire to protect American technology," Commerce Secretary Wilbur Ross said in a statement to The Journal on Sunday. "All possibilities that would better protect American technology, including potential changes to export controls, are under review."

The new curbs, which are designed to protect US intellectual property — something President Donald Trump's trade adviser Peter Navarro described last week as the country's "crown jewels of technology" — would most likely be brought about under the International Emergency Economic Powers Act of 1977. The law gives the president extraordinary powers in times of "unusual and extraordinary threat" to the US economy.

The proposed new curbs on Chinese ownership come at a time when the US and China are already involved in an escalating conflict over trade.

China announced tariffs on $50 billion worth of imports from the US last week in response to Trump's tariffs on Chinese goods set to take effect in July.

Trump has also threatened to place tariffs on the European automotive sector, which would mark another major move in the developing global trade conflict.

Trump in May directed the Commerce Department to launch an investigation into imported autos, similar to the procedure that led to the recent tariffs on steel and aluminium imports. While the results of that investigation are still weeks away, Trump raised the specter of tariffs on Twitter.

"Based on the Tariffs and Trade Barriers long placed on the US and it great companies and workers by the European Union, if these Tariffs and Barriers are not soon broken down and removed, we will be placing a 20% Tariff on all of their cars coming into the US," Trump tweeted on Friday. "Build them here!"

You can read The Wall Street Journal's full story on the proposed new rules here.