The Holocaust scholar was dragged from an elevator and roughed up during a peace conference at a San Francisco hotel on Feb. 1, according to police. The author was not injured.
"Until today they used words; now they have switched to violence," Wiesel told Milan-based daily Corriere della Sera. "Their numbers are growing by the day."
The assailant fled after Wiesel began to scream, and police have opened a criminal investigation.
The 78-year-old Holocaust survivor said the incident shook him and that, for the first time since World War II, he felt he was being personally targeted.
"I feared for my life in a way that hadn't happened to me since 1945, before the end of the war," he told Corriere.
Wiesel said he hoped a posting on an anti-Semitic Web site in which a man claimed responsibility for the attack would help investigators make an arrest.
"It is crucial to discover if he was a madman who acted alone or the follower of a larger organization," he said.
Wiesel, who survived the Nazi death camps at Auschwitz and Buchenwald, has worked for human rights in many parts of the world and was awarded the Nobel Peace Prize in 1986.
In the interview with Corriere, he urged countries to take a harsher stance against those who argue that millions of Jews did not die at the hands of the Nazis.
"My incident shows a global trend; if society doesn't act immediately against these individuals it will end up encouraging others to do the same," he said. "Every time I make a speech somewhere in the world there is a group of deniers in that place waiting for me."