Prosecutors say the activists, who will stand trial next week, used threats, intimidation and cyber attacks against employees of Huntingdon Life Sciences, a British company with operations in East Millstone, New Jersey, with the intention of driving it out of business.

The six, members of a group called Stop Huntingdon Animal Cruelty (SHAC), are charged under the Animal Enterprise Protection Act, amended in 2002 to include "animal enterprise terrorism," which outlaws disrupting firms like Huntingdon.

If convicted, the group and its accused members face a maximum $250,000 fine and three years in prison.

SHAC argued that the charges are a violation of free-speech rights and it is the victim of a government crackdown on dissent. "This is a frightening step in the Bush administration's path to war on domestic dissidence," the group said on its Web site.

The defendants are also charged with interstate stalking, which carries a maximum sentence of five years in prison and $250,000 fine, and with conspiracy to engage in interstate stalking, carrying the same penalty.

The list of potential defense witnesses includes actress Kim Basinger, who joined a protest outside a Huntingdon laboratory in Franklin, New Jersey to try to stop such companies using animals to test their pharmaceutical products.

The group also targeted other companies that did business with Huntingdon. Those firms were swamped with telephone calls and e-mail blitzes intended to clog their computer systems, the indictment said.

Other alleged incidents include overturning a Huntingdon employee's car in the driveway of his New Jersey home and the destruction of putting greens at the Meadowbrook Golf Club in Long Island, New York, where some Huntingdon employees held memberships.

Those charged are Kevin Kjonaas, 27, president of SHAC; Lauren Gazzola, 26, the group's campaign coordinator; Jacob Conroy, 29; Joshua Harper, 30; Darius Fullmer, 28; and Andrew Stepanian, 26. They all deny the charges.

Opening arguments before Judge Mary Cooper of U.S. District Court in Trenton, New Jersey, are expected early next week. Jury selection began Wednesday.