(Adds Wolf comments on extremism and election security)
By Ted Hesson and Mark Hosenball
WASHINGTON, Sept 23 (Reuters) - White supremacist groups have posed "the most persistent and lethal threat" of violent extremism in the United States in recent years, acting U.S. Homeland Security Secretary Chad Wolf said at a congressional hearing on Wednesday.
U.S. President Donald Trump and his top officials have sought to promote a law-and-order message amid nationwide racial justice protests over the summer, some of which became violent. Wolf has warned of the threat of anarchists or left-wing anti-fascist agitators, but faced criticism from liberal groups for not acknowledging the danger posed by white supremacists.
Wolf's remarks follow a U.S. Department of Homeland Security (DHS) whistleblower complaint earlier this month that alleged Wolf attempted to play down U.S. white supremacist activity.
Wolf rejected the whistleblower allegations during his confirmation hearing before the Senate Homeland Security and Governmental Affairs Committee on Wednesday, calling the claims "patently false" and "a fabrication."
Daryl Johnson, a former DHS analyst, said Wolf's comments acknowledging the threat of white supremacist groups was significant. "Now, let's see that talk turn into action by devoting more resources," he said.
The U.S. Justice Department on Monday threatened to revoke federal funding for New York City, Seattle and Portland, Oregon, saying the three liberal cities were allowing anarchy and violence on their streets.
During the hearing, Wolf reiterated his position that people with an "anarchist sort of ideology" had targeted a federal courthouse in Portland during clashes between police and protests in July.
FBI Director Christopher Wray said during a congressional hearing last week that the FBI is conducting multiple investigations into violent domestic extremists following months of street protests against racism and police brutality.
Wray said the largest "chunk" of investigations were into white supremacist groups. (Reporting by Ted Hesson, Mark Hosenball and Lisa Lambert; Editing by Chizu Nomiyama, Jonathan Oatis and Diane Craft)
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