The state was issuing an arrest warrant for James C. Kopp, 44, of St. Albans, Vt.
"We have probable cause to believe this man, James Kopp, is responsible for the death of Dr. Bernard Slepian," FBI agent Bernard Tolbert said.
Kopp, whose whereabouts are unknown, had been sought as a material witness since shortly after the doctor was shot to death while in his kitchen by a single bullet from a high-powered rifle Oct. 23.
The federal charge carries a maximum penalty of life in prison and a $250,000 fine, U.S. Attorney Denise O'Donnell said.
Kopp also faces a federal charge of violating the Freedom of Access to Clinic Entrances Act by using deadly force, authorities said Thursday.
|Dr. Barnett Slepian (AP)|
At a news conference Thursday, investigators would not divulge the specific evidence against Kopp. However, a high-powered rifle was found earlier this year buried in the woods behind Slepian's home.
Investigators have said they are considering a theory that the weapon was buried in advance of the shooting, with the killer digging it up to fire the shot before reburying it and fleeing.
Authorities have said Kopp's 1987 black Chevrolet Cavalier was spotted in Slepian's suburban Amherst neighborhood in the weeks before the shooting. The vehicle was found abandoned at New Jersey's Newark International Airport in December.
A hair found near Slepian's home was linked to Kopp through DNA testing, authorities said.
Nicknamed the "Atomic Dog" in anti-abortion circles, Kopp had been arrested in several states since 1990 for protesting abortion.
In response to the new charges, Canadian officials confirmed that Kopp is a suspect in sniper shootings that injured abortion doctors in November in Vancouver, British Columbia; Winnipeg, Manitoba; and Hamilton, Ontario.
Kopp is now the second anti-abortion activist being sought by the FBI in connection with a fatal attack.
Eric Rudolph has been on the run since the January 1998 bombing of a Birmingham, Ala., abortion clinic that killed an off-duty police officer and severely wounded a nurse. He also is charged in three Atlanta attacks, including the 1996 Olympic bombing that killed one person.
Reported By Carolyn Thompson