WASHINGTON — The Russian military buildup at the Ukraine border and in Crimea could provide enough forces for a limited military incursion, the C.I.A. director, William J. Burns, told senators on Wednesday as he and other senior officials outlined a range of threats facing the United States.
Russia could simply be sending a signal to the United States or trying to intimidate the Ukrainian government, but it had the abilities in place to do more, Mr. Burns told the Senate Intelligence Committee.
“That buildup has reached the point that it could provide the basis for a limited military incursion, as well,” Mr. Burns said. “It is something not only the United States but our allies have to take very seriously.”
Mr. Burns testified alongside Avril D. Haines, the director of national intelligence, and other officials about an array of threats from global powers like Russia and China as well as challenges that have been less of a focus of intelligence agencies in the past, including domestic extremism and climate change.
In its annual threat assessment report, released Tuesday ahead of the hearing, the intelligence community said that China’s push for global power posed a threat to the United States through its aggression in its region, its expansion of its surveillance abilities and its attempts to dominate technological advances.
Russia has also pushed for a sphere of influence that includes countries that were part of the Soviet Union, like Ukraine, the report said.
Both China and Russia, however, wanted to avoid direct confrontation with the United States, the report said.
Mr. Burns said the Russian actions have prompted internal briefings as well as consultations with allies. President Biden’s call on Tuesday to President Vladimir V. Putin of Russia was intended to “register very clearly the seriousness of our concern,” Mr. Burns said.
The United States has been tracking the Russian troops for some time, at least since late March. American officials have said privately that the Russians have done little to hide their troop buildup, unlike in 2014 when they first attacked Ukraine. That has convinced some, but not all, officials briefed on the intelligence that the Russian activities may be mostly for show.
“They could actually be going into a series of exercises starting anytime, or they could, if they chose to, perhaps do a limited objective attack,” said Lt. Gen. Scott D. Berrier, the director of the Defense Intelligence Agency. “We don’t know what the intent is, right now.”
Both Russia and China have been blamed for conducting cyberoperations that compromised broad sections of the software supply chain. Lawmakers asked Ms. Haines and Gen. Paul M. Nakasone, the director of the National Security Agency, about the Russian hacking, which penetrated nine federal agencies, and another by China that compromised Microsoft Exchange servers. The Biden administration is expected to respond to the Russian hacking soon, most likely with sanctions and other measures.
Ms. Haines said Russia used hackings to sow discord and threaten the United States and its allies. “Russia is becoming increasingly adept at leveraging its technological prowess to develop asymmetric options in both the military and cyberspheres in order to give itself the ability to push back and force the United States to accommodate its interests,” she said.
Lawmakers also raised the issue of a series of mysterious episodes that have injured diplomats and C.I.A. officers overseas. Some former officials believe Russia is behind the episodes, which they have called attacks.
Mr. Burns said he was working with his colleagues to ensure better medical care for C.I.A. officers. He also said he was working to “get to the bottom of the question of what caused these incidents and who might have been responsible.”
Questions on China dominated the earlier Senate confirmation hearings for Ms. Haines and Mr. Burns, and lawmakers again pressed on Wednesday for assessments on China and its efforts to steal American technology. Ms. Haines outlined how China uses technological might, economic influence and other levers of power to intimidate its neighbors.
“China is employing a comprehensive approach to demonstrate its growing strength and compel regional neighbors to acquiesce to Beijing’s preferences,” she told senators.
The F.B.I. director, Christopher A. Wray, also emphasized the threat from China. “We’re opening a new investigation into China every 10 hours,” he said of the bureau, “and I can assure the committee that’s not because our folks don’t have anything to do with their time.”
Biden administration officials have said that they want the intelligence agencies to take a wider view of national security threats.
Ms. Haines noted that another recent intelligence report, on global trends, highlighted how the coronavirus pandemic and climate change, along with technological change, were testing “the resilience and adaptability” of society. The “looming disequilibrium,” she said, compels intelligence agencies to broaden their definition of national security.
But at least one lawmaker, Senator Richard M. Burr, Republican of North Carolina, also asked a more practical question: How many intelligence officers have received coronavirus vaccines?
Mr. Burns said 80 percent of the C.I.A. work force was fully vaccinated and another 10 percent have had their first shot. He said all C.I.A. officers serving overseas “have the vaccine available to them directly.”
Mr. Wray was unable to give an estimate of how many of his agents had received a shot, saying that the vaccination rates varied in field offices in different states. Ms. Haines said 86 percent of her work force had had at least one shot, with a “fair percentage” being fully vaccinated. General Nakasone also had no estimate but said a vaccination center had been set up at Fort Meade, Md., where the National Security Agency’s headquarters is.
Lawmakers have also been pressing intelligence agencies to help examine the problem of domestic extremism. Senator Mark Warner, Democrat of Virginia and the chairman of the intelligence committee, linked the rise of domestic extremism to the same trends promoting disinformation produced by Russia and others. And he said he wanted the intelligence chiefs to outline how they could help provide better warnings of potential violence like the Jan. 6 attack on the U.S. Capitol.
Social media has helped disinformation from domestic extremist groups spread with more speed and efficiency than ever before — much the same as Russia and other nations have used it to spread falsehoods, Mr. Wray said.
“Social media has become, in many ways, the key amplifier to domestic violence extremism, just as it has for malign foreign influence,” he said. “There is all sorts of stuff out there on the internet that poses as facts, which just isn’t.”
The isolation caused by the pandemic, Mr. Wray continued, had increased the public’s susceptibility.
The intelligence chiefs’ hearing was the first since early 2019, when they contradicted President Donald J. Trump’s rosier public statements, prompting Mr. Trump to criticize his appointees publicly, telling them to “go back to school.” Mr. Trump’s last director of national intelligence, John Ratcliffe, chose not to release a threat assessment or testify before Congress last year.