WASHINGTON — Once in office, President-elect Joe Biden will punish Russia for its suspected cyberespionage operation against the United States with financial sanctions and measures to hobble the Kremlin’s ability to launch future hacks, hischiefofstaffsaidSunday, as a GOP senator criticized PresidentDonaldTrumpfor havinga“blindspot” whenit comes to Moscow.

“Those who are responsible are going to face consequences for it,” said Biden chief of staff Ron Klain. “It’s not just sanctions. It’s also steps and things we could dotodegradethecapacityof foreign actors to repeat this sort of attack or, worse still, engageinevenmoredangerous attacks.”

The head of the cybersecurity firm FireEye, which disclosed that it had been targeted by the spying attempt, said it was clear the foreign intrusions were not “one and done” and suggested there was little timetosparebeforethenext one.

“These attacks will continue to escalate, and get worseifwedonothing,” said CEO Kevin Mandia.

Cybersecurityexpertsand U.S. officials such as Secretary of State Mike Pompeo havebeenclearoverthepast weekthattheybelieveRussia was behind the massive hack that infiltrated over 40 federal agencies, including thedepartmentsofTreasury, Energy and Commerce, as wellasgovernmentcontractors.

But Trump over the weekend cast doubt on that assessment, suggestingwithoutevidencethatChinamay bebehindtheintrusionsand minimizingtheimpact.“The Cyber Hack is far greater in the Fake News Media than in actuality. I have been fully briefed and everything is well under control,” Trump tweeted, contradicting his own cybersecurity agency, Ron Klain, left, the incoming chief of staff forJoe Biden, said the president-elect will look to hobble Russia from carrying out future cyberattcks. MARKWILSON/GETTY 2014 which described the hacks as a “grave” threat.

On Sunday, Sen. Mitt Romney, R-Utah, blasted Trump for putting the U.S. at continuing risk.

“Russia acted with impunity,” he said. “They didn’t fear what we would be able to do from a cybercapacity.

They didn’t think that our defensesystemswereparticularly adequate. And they apparently didn’t think that we would respond in a very aggressive way.”

“I think we’ve come to recognize that the president has a blind spot when it comes to Russia,” Romney added, urging an immediate response and calling cyberspace the “warfare of the future.”

While Trump downplayed the impact of the hacks, the Cybersecurity and Infrastructure Security Agency has said it compromised federal agencies as well as “critical infrastructure.”

Homeland Security, the agency’s parent department, defines such infrastructureasany“vital” assets to the U.S. or its economy, a broad category that could include power plants and financial institutions.

It’s not clear exactly what the hackers were seeking, but experts say it could include nuclear secrets, blueprints for advanced weaponry, COVID-19 vaccine-relatedresearchand information for dossiers on government and industry leaders.

Still, itmaytakemonthsto kick elite hackers out of the U.S. government networks they have been quietly riffling through since as far back as March. Christopher Krebs, former director of CISA, highlighted the challenges ahead as Trump dismisses the threat and Biden prepares for his Jan.

20 inauguration.

“Thefederalcivilianagencies, the101civilianagencies, are not really optimized for defense right now,” Krebs said. “And what that means is, there’s a lot of old antiquated, legacy IT systems that are hard to defend.

Plus, the authorities are not in place for teams like CISA to really get out there and aggressively root out adversaries.”

Klain and Mandia spoke on CBS’ “Face the Nation,”

Krebs was on CNN’s “State of the Union,” and Romney was on CNN and NBC’s “Meet the Press.”