Chinese hackers are positioning themselves in US critical infrastructure in the event of a clash with the United States, a top American cybersecurity official said on Friday.

Morgan Adamski, the executive director of US Cyber Command, said ongoing Chinese-linked cyber operations are aimed at gaining “an advantage in the event of a major crisis or conflict with the US”

Adamski made the comments to researchers at the Cyberwarcon security conference in Arlington, Virginia. On Thursday, US Senator Mark Warner told the Washington Post that a suspected China-linked hack on US telecommunications firms was “the worst telecom hack in our nation’s history – by far.”

That cyberespionage operation, dubbed “Salt Typhoon,” has included stolen call records data, the compromise of communications of top officials of both major US presidential campaigns before the Nov. 5 election, and telecommunications information related to US law enforcement requests, the FBI said in a recent statement.

Beijing routinely denies cyber operations targeting US entities. The Chinese Embassy in Washington did not immediately respond to a request for comment.