By Jon Donnison
BBC News, Washington
Richard Poplawski, a member of a racist group, killed three police officers
America could be facing a surge in right-wing extremism, according to a new US government report.
The Department of Homeland Security study says the election of America's first black president and the economic slump has helped racist groups recruit.
But the report says no specific attacks are being planned by extremists.
Some moderate conservatives fear the administration could use the report as an excuse to tighten gun laws and restrict freedom of speech.
The report says that high unemployment figures and home foreclosures have created a climate similar to the early 1990s when white supremacists saw a growth period.
That resurgence was stifled in 1995 after an FBI crackdown on extreme right groups following the Oklahoma City bombings carried out by Timothy McVeigh.
Some extreme right websites reported a surge in membership immediately after Barack Obama's election.
The Homeland Security study says the threat posed by what it calls "lone wolves" and "small terrorist cells" is more pronounced that in previous years.
It cites an example two weeks ago when three police officers were shot dead in Pittsburgh by Richard Poplawski, who had been a member of a white supremacist group.
Some more moderate conservatives have criticised the Homeland Security study. They believe the White House could use it to justify tougher gun laws and restrictions on conservatives' freedom of speech.
The issue is being keenly debated on right-wing blogs and talk shows.
Radio talk show host Michael Savage, who runs the website Savage Nation, is asking his readers whether Homeland Security Secretary Janet Napolitano should step down for "targeting loyal, patriotic Americans as possible terrorists".