Mayor Nutter yesterday used the occasion of an interfaith service memorializing Philadelphia police Sgt. Timothy Simpson to reiterate "a firm commitment to make the city safe."

Simpson, 46, a 20-year veteran of the department, became its fourth member to die on the job this year when his police cruiser was broadsided Nov. 17 in Port Richmond. William Foster, 41, of Levittown, was charged with third-degree murder. Cops said that Foster was fleeing from officers after a drug buy when his car slammed Simpson's cruiser.

Yesterday, in the Cathedral Basilica of Ss. Peter and Paul, Simpson's heroism was recalled by Nutter, who said that his administration would not rest until Philadelphia was made safer for citizens and officers.

Nutter said that he did not have an explanation for the city's violence, but he made "a firm commitment to make the city safe, and to make sure that police officers are safe going about their work."

"We will never slow down, back off or rest until we make this a safer city," Nutter said in hushed, somber tones. "And I will not personally rest until that time."

Nutter said that Simpson "lived commitment every day of his life."

"For police officers, they understand that when they leave their house, it could very well be the last time," Nutter said, surrounded by religious leaders of various faiths. "It takes a very special person to take on that task.

"I didn't know him personally, but I knew him to be a hero, son and father," Nutter said of Simpson. "He was the consummate police officer."

Nutter said that he could not forget Simpson and other officers killed in the line of duty. "I will never forget the sacrifice of Sergeant Simpson on that cold November night," he said. "We will honor his memory forever."

Everett Gillison, the deputy mayor for public safety, said that the memorial service was "a period for us to reflect on what public service is about."

"We have this service for the 20 years of service that Tim gave," Gillison said, before Nutter presented the Simpson family with a proclamation and a flag. "We are always reminded that what we do for others is how we will be remembered."