The U.S. intelligence community took aim at China during its annual assessment of worldwide threats, accusing the East Asian giant of blistering cyberattacks that are the foundation of a prolonged espionage campaign.

In what is considered the seminal yearly report of foreign threats to the United States, leaders from six high profile intelligence agencies warned that the “post-World War II international system is coming under increasing strain amid continuing cyber” threats, among other avenues of attack.

“China, Russia, North Korea and Iran are advancing their cyber capabilities, which are relatively low-cost and growing in potential severity,” Director of National Intelligence Dan Coats told the Senate Intelligence Committee. “As the world becomes increasingly interconnected, we expect these actors, and others, to rely more and more on cyber capabilities when seeking to gain political economic and military advantages over the United States and its allies and partners.”

China topped the list of cyber threats facing the United States.

“China remains the most active strategic competitor responsible for cyber espionage against the U.S. government, corporations and allies,” the accompanying document read. “Beijing will authorize cyber espionage against key U.S. technology sectors when doing so addresses a significant national security or economic goal not achievable through other means.”

“The Chinese counterintelligence threat is more deep, more diverse, more vexing, more challenging, more comprehensive and more concerning than any other counterintelligence threat that I can think of,” FBI Director Christopher Wray told lawmakers.

Questions emailed to the Chinese embassy in Washington D.C. were not returned.

The sharp rhetoric regarding Beijing comes just one day after the Justice Department accused Chinese telephone conglomerate Huawei of fraud and stealing sensitive trade secrets. American intelligence officials have previously warned against using Huawei phones out of fears it was a sieve for Chinese intelligence. In August, Fifth Domain reported that Huawei phones are vulnerable to hacking.

“China had a remarkable rise in capabilities that are stunning. A significant amount of that was achieved through stealing information of our companies,” Coats, the intelligence chief, warned.

The American intelligence community’s assessment of Chinese digital aggression comes during a trade war between the two countries, and after an agreement between the two nations to limit the use of cyberattacks for business intelligence broke down.

Experts say that China frequently uses publicly available tools, which are relatively cheap, during their cyberattacks. Their attack patterns are also easy to emulate, and experts say that hackers are increasingly making their viruses look like they came from China.

The intelligence chiefs’ briefing also offered insights into how the cyberthreat against the United States is growing more complex.

Wray told lawmakers that nation-states are working with criminal hackers in a “form of outsourcing that makes it even more of a menace.”

“Foreign cyber criminals will continue to conduct for-profit, cyber-enabled theft and extortion against U.S. networks,” the 2019 intelligence assessment said.

However in the immediate future, Coats warned that protecting the 2020 presidential elections represent “a top priority for the intelligence community.”

“We assess that foreign actors will view the 2020 U.S. elections as an opportunity to advance their interests,” Coats said.

The intelligence community assessed that the 2018 midterm elections were targets of foreign nations. Both Democratic and Republican party officials were targets of cyberattacks or misinformation, U.S. officials said.

During his testimony to lawmakers, Coats said election security would continue to be a top focus for the intelligence community.

“On the heels of our successful efforts to protect the integrity of the 2018 midterm elections, we are now focused on incorporating lessons learned in preparation for the 2020 elections.”