A senior U.S. State Department official said Wednesday that Beijing’s support for Moscow’s defense industry comes directly from the top leadership of the People’s Republic of China, or PRC. The official also pointed out that chips supplied by China have significantly bolstered Russia’s battlefield capabilities in its war against Ukraine.

For months, U.S. officials have accused the PRC of actively aiding Russia’s war effort. Washington has sanctioned Chinese firms providing crucial components to Russia’s defense industry.

On Wednesday, Deputy Secretary of State Kurt Campbell told lawmakers that the U.S. had been slow to fully grasp the “absolute intensity of engagement” between Russian President Vladimir Putin and Chinese President Xi Jinping.

“The most worrisome thing is that it [China’s support for Russia] comes from the very top,” Campbell said during a House Foreign Affairs Committee hearing.

He added that “chips, some design features, some capacities associated with the making of explosives” have been enhancing Russia’s battlefield operations.

“We see the role of UAVs [unmanned aerial vehicles, or drones] and other capacities that are penetrating the Ukrainian airspace. Much of that has been supported surreptitiously by China, and it raises real concerns.”

Chinese officials rejected Washington’s accusations, asserting that the U.S. should not “smear or attack the normal relations between China and Russia” or infringe upon “the legitimate rights and interests” of China and its companies.

Beijing also continues to call for peace talks between Russia and Ukraine leading to a political settlement, more than two and a half years into the war.

Some members of Congress have urged President Joe Biden’s administration to sanction Chinese banks for supporting Russia’s war on Ukraine.

“We’ve put many of their [PRC] financial institutions on watch. … We’ve got to have Europeans with us. I think we’re beginning to make headway,” said Campbell.

The State Department’s second-ranking diplomat said the challenges posed to the U.S. by the PRC exceed those of the Cold War, following a large-scale joint military exercise between China and Russia.

Dubbed “Ocean-2024,” the massive naval and air drills spanned a huge swath of ocean and involved more than 400 naval vessels, at least 120 military aircraft and upward of 90,000 troops, according to the Russian Defense Ministry.

Without naming specific countries, Chinese officials said that the military exercise between the two allies, which concluded Monday, was intended to address joint threats.

Mao Ning, a spokesperson for China’s Ministry of Foreign Affairs, elaborated during a recent briefing in Beijing, saying, “China and Russia [held] this joint exercise in order to deepen their mil-to-mil strategic coordination and strengthen the capacity to jointly address security threats.”