"Crimes are crimes, no matter who does them," the statement reads over pictures of Obama and his predecessor George W. Bush due to appear in the New York Review of Books.
The statement, published as a paid advertisement, accuses Obama, who was elected in 2008 with the enthusiastic support of US liberals, of continuing Bush's controversial approach to human rights in Iraq and Afghanistan, and in domestic security.
It takes aim especially at Obama's decision -- reported by US officials -- to authorize the killing of a radical Islamic cleric and US citizen Anwar al-Awlaki, who is accused of ties to Al-Qaeda in Yemen.
"In some respects this is worse than Bush," the statement says. "First, because Obama has claimed the right to assassinate American citizens whom he suspects of 'terrorism,' merely on the grounds of his own suspicion or that of the CIA, something Bush never claimed publicly."
Among the signatories are linguist Noam Chomsky, " " actor James Cromwell, actor Mark Ruffalo and prominent Bush-era anti-war protestor . By midday Thursday there were 1,804 signatures.