Republican US Senator Mitt Romney said a widespread data breach across the US government was "extraordinarily damaging" and that President Donald Trump has a "blind spot" when it comes to Russia, which US officials believe was behind the hack.
"We've come to recognize that the president has a blind spot when it comes to Russia," Romney said on NBC's "Meet the Press," one of a series of Sunday morning TV interviews.
US officials and researchers say they believe at least half-a-dozen US government agencies have been infiltrated and thousands of companies infected with malware in what appears to be one of the biggest such hacks ever uncovered.
Trump only acknowledged the hacking on Saturday almost a week after Reuters first reported it, downplaying its importance and questioning whether the Russians were to blame.
Revelations of the hack come at a vulnerable time as the US government grapples with a contentious presidential transition and the coronavirus health crisis.
US Senator Mark Warner, the top Democrat on the Senate Intelligence Committee, said on ABC that the cyberattack could be ongoing and that officials had not yet determined its full scope.
Both Warner and Romney said the United States must respond to the incident.
The team of President-elect Joe Biden, a Democrat, will consider several options to punish Russia over its suspected role once he takes office, from financial sanctions to cyberattacks on Russian infrastructure, people familiar with the matter say.