Ms. Berenson's parents, Mark and Rhoda Berenson, have urged President Alejandro Toledo to pardon their daughter, who was convicted last June of aiding the Túpac Amaru rebels in their war against the government in the 1990's. She was sentenced to 20 years in prison.

Those proceedings were a retrial for Ms. Berenson, who was first convicted on the charges in 1996 and sentenced to life in prison by hooded judges in a military tribunal.

Justice Minister Fernando Olivera said today that Ms. Berenson was now "a proven terrorist, convicted in a new trial with all the guarantees."

Speaking on radio, Mr. Olivera said, "The sentence must be served because the law should be applied equally to everyone." He added, "The truth is there is nothing more to talk about, and there is no presidential pardon under consideration."

Ms. Berenson, 32, said Monday that she had joined more than 500 jailed rebels in a nationwide hunger strike to protest the harsh conditions of their confinement and their convictions under tough laws enacted by former President Alberto K. Fujimori to combat two radical rebel groups.

Ms. Berenson's parents, reached by phone in New York, said they were worried about the health of their daughter, who has suffered in the high-altitude prisons where she has been housed. In the hunger strike, Ms. Berenson will drink only liquids. "It's distressing for us to know that she's doing it," Mr. Berenson said.

In a statement on a Web site maintained by her parents, Mr. Berenson said the hunger strike aimed to highlight abuses under Mr. Fujimori's government, which collapsed 16 months ago in a corruption scandal.

The hunger strikers, men and women convicted of being members of Shining Path and the Túpac Amaru Revolutionary Movement are demanding that the government close three prisons, abolish the antiterrorism legislation under which they were convicted and grant them retrials.

Mr. Toledo's government has rejected the demands. "We are not going to permit a coordinated action to weaken the democratic authority," Mr. Olivera said last week.

In Peru there is little sympathy for the jailed rebels, who are widely viewed as terrorists who caused thousands of deaths in a conflict that lasted nearly 20 years. Most Peruvians see Ms. Berenson as guilty of collaborating with the Túpac Amaru movement, which is best known for its 1996 takeover of the Japanese ambassador's residence.

Richard A. Boucher, the State Department spokesman, said today in Washington that the United States believed that Ms. Berenson had received due process in her appeal. Ms. Berenson's lawyer "did ensure that his client received all the rights and protections that can be afforded under Peruvian law, " he said.

Ms. Berenson, a former Massachusetts Institute of Technology student, was arrested In Lima in November 1995, hours before the police raided a four-story house she rented. At the house, the police met resistance from Túpac Amaru rebels inside. The authorities later found 8,000 rounds of ammunition and 3,000 sticks of dynamite.

Ms. Berenson argued that she was not aware that her housemates were rebels.