Top law enforcement officials say the biggest domestic terror threat comes from white supremacists.

Attorney General Merrick B. Garland and Homeland Security Secretary Alejandro N. Mayorkas told senators on Wednesday that the greatest domestic threat facing the United States came from what they both called “racially or ethnically motivated violent extremists.”

“Specifically those who advocate for the superiority of the white race,” Mr. Garland told the Senate Appropriations Committee.

The cabinet secretaries’ comments reflected a dramatic shift from the tone of the Trump administration, which deliberately downplayed the threat from white supremacists and similar groups, in part to elevate the profile of what former President Donald J. Trump described as violent threats from radical left-wing groups.

Last year, the former head of Homeland Security’s intelligence branch filed a whistle-blower complaint in which he accused the department of blocking an intelligence report about the threat of violent racism and described white supremacists as having been the deadliest domestic terrorists in recent years.

“The department is taking a new approach to addressing domestic violent extremism, both internally and externally,” Mr. Mayorkas told senators on Wednesday.

While the Justice and Homeland Security departments have long been involved in countering violent extremism inside the country, Biden administration officials have said the Jan. 6 pro-Trump riot at the Capitol brought an urgent need to focus more on domestic extremism.

But Senate Republicans did not share that focus. The top Republican on the committee, Senator Richard C. Shelby of Alabama, said that Democrats were politicizing the issue by painting domestic violent extremists as coming from the far right. He equated the riots to the protests against police violence during the summer of 2020.

Other Republicans on the committee grilled the attorney general and homeland security chief on border security and other immigration issues.

The Justice Department is leading the investigation into the Jan. 6 riots and has arrested more than 430 people across the country, Mr. Garland said. As recently as last week, prosecutors began informally negotiating plea deals. Some of the defendants have been fighting the charges.