NEW YORK -- Richard Williams, the father of the world's top two women's tennis players in Serena and Venus Williams, has threatened to kill the man who has followed Serena around the world if he harms his 20-year-old daughter.

Albrecht Stromeyer, 34, of Germany was being held at Rikers Island following his arrest Saturday on three misdemeanor counts of stalking at the National Tennis Center after watching Serena practice during the U.S. Open.

An Immigration and Naturalization Service detainer was also placed on Stromeyer on Sunday afternoon. The detainer means that even if Stromeyer posts his $3,000 bail, he would not be released. His next appearance at the Queens Criminal Court is set for Thursday.

"I don't think the guy is ever going to give up," Richard Williams told the New York Daily News on Monday. "At some point ... something very tragic could take place. Would (anything) stop me from killing this guy if he did something to one of my daughters?

"I do not think all the police officers in the world could stop me."

A police officer recognized Stromeyer from a photograph distributed by Williams' management as Stromeyer was peering through a fence at the U.S. Tennis Center while Serena Williams warmed up for her third-round match against France's Nathalie Dechy.

Stromeyer has pursued Williams at tournaments around the world and has made numerous attempts to contact her by phone and e-mail.

In early July, Wimbledon Magistrates Court ordered Stromeyer to stay out of trouble for 12 months after he smashed a police camera near the tournament venue.

In May, Stromeyer, who lives with his parents, was extradited from Italy to face charges of stalking Williams.

Two months earlier, Stromeyer walked into an Arizona resort where Williams was playing and asked to see her. When he was turned down, Stromeyer began undressing in front of the desk clerk. He was charged with disorderly conduct and indecent exposure.

"I think this guy is sick," Richard Williams told the Daily News. "A sick person is not capable of thinking correctly and they are capable of doing anything."

"The bail is so low, I think that encourages him to keep doing what he's doing. It makes me wonder, 'Could he hurt Serena?' A Williams is the most precious commodity to a Williams. A Williams would die for a Williams."

Erich Stromeyer, Albrecht's father, told the newspaper from his Frankfurt home that he has pleaded with his son to give up his obsession with the tennis star.

"He has a mental problem," the retired banker said. "I told him so many times to drop it. I told him Serena Williams has no interest in him.

The elder Stromeyer added that his son poses no danger to Serena Williams, but "he knows the risk" of allegedly stalking Williams. "He either does not understand it or he doesn't want to understand it."