(CNN) -- The Iranian government's efforts to suppress anti-government demonstrations will only increase the opposition's will, Nobel Peace Prize winner Shirin Ebadi told CNN Monday.
"The heavier the crackdown, the more determined people will be to protest, as events in the past have shown. The higher levels of crackdown have radicalized the people," the Iranian lawyer and human rights activist said.
But sanctions on Iran's nuclear program will not damage the Islamic regime -- in fact, they "only increase the nationalistic sentiments of the Iranian people," she warned.
Sanctions should "target issues that impact the government and not those that affect the people. For example, recently the Iranian government, it has been said, will import anti-riot tanks. Not from the United States but from China and Russia," Ebadi said.
"So sanctions should aim to stop these transactions, not to enhance the ability of the Iranian state to increase the crackdown on the people," Ebadi said, speaking to CNN's Zain Verjee by telephone.
Ebadi is in the United Kingdom but did not say exactly where in order to protect her security. She has not been in Iran since protests erupted in the wake of the disputed June 12 presidential election.
She said she hoped the Iranian parliament would vote to allow U.S. Senator John Kerry to visit the country, but did not expect great results even if he is allowed to make the trip.
Kerry, the chairman of the Senate Foreign Relations Committee and the 2004 Democratic candidate for president, has requested a visa to enter Iran.
"A visit by Mr. Kerry would be a positive step," Ebadi said. "However, having said that, I think that he will return with empty hands because the government has shown in the past five years that it will not be open to negotiation."
Ebadi, who won the 2003 Nobel Peace Prize, also expressed concern for her sister, who was detained a week ago. She said she had not had any contact with her sister since she was seized by authorities.
"Since the evening when they went to take her I have not spoken or heard of her," Ebadi said. "I would say that they have taken her hostage and since then I don't know of her whereabouts and I am very concerned about her health."
Ebadi told CNN a week ago that three men and a woman arrived at the Tehran home she shared with her sister, searched the house and seized Nushin Ebadi, 47, and her computer.
"They have detained her so I stop my work," Shirin Ebadi, 62, told CNN's Reza Sayah by telephone on December 28. "She has done nothing wrong. She's not involved in human rights work, and she's never participated in any of the protests."
"Not only does my sister not do any human rights work, she doesn't do any cultural work either," Ebadi said in the earlier call. "They only took her because of me."
Nushin Ebadi and her husband are professors of dentistry at Azad University in Tehran, Shirin Ebadi said, and Nushin Ebadi's husband also has a private dental practice.
The authorities have harassed other members of Ebadi's family as well, she said.
"My husband, my brother and my sister were summoned on several occasions to the intelligence ministry and told that if I did not cease my human rights activities that they would be arrested," she said Monday.
"I thought they did not mean what they said. But unfortunately, they went to my sister's house and arrested her, and have said that unless these activities cease, they will continue arresting other members of my family."
Ebadi left Iran for a conference in Spain the day before June presidential elections that sparked violent protests. Friends, she said, warned her not to return to Tehran.
CNN's Erin McLaughlin in London, England, contributed to this report.