Physician LeRoy Carhart wants to continue providing third-term abortions after the brazen slaying of his friend and colleague George Tiller, but the Nebraska doctor doesn't have anywhere to perform them — and he's one of only a handful of providers who will.

Tiller's Wichita, Kan., clinic was shuttered Sunday after the 67-year-old physician was gunned down at his church. His family said Tuesday that they were unsure when it would reopen, posing a problem for Carhart, who wants to carry on his friend's mission.

Carhart, 67, is one of a handful of remaining doctors in the United States who perform third-trimester abortions, and it is uncertain if a new generation of providers will take over the cause. Schools and universities don't offer many programs to train physicians on how to perform the procedure, and Carhart said younger doctors who might be interested in stepping forward are afraid they or their families will be harmed.

Tiller's slaying underlined that fear. On Tuesday, Kansas authorities charged 51-year-old Scott Roeder, a staunch abortion opponent, with first-degree murder in Tiller's death.

"Dr. Tiller and I and all our friends know that tomorrow is never a given," Carhart told The Associated Press. "I think what we have to do is not let this loss of his life affect our goals in life, No. 1, and we need to do things so he's never forgotten."

Carhart, a vocal abortion rights advocate who has been at the epicenter of the debate on what abortion foes call partial-birth abortions, first met Tiller more than 20 years ago and began working at the Wichita clinic a decade ago. He said he regularly traveled to Kansas for a few days every third week. He only performs third-term abortions at Tiller's clinic.

Carhart drew national protests from abortion opponents after he filed a lawsuit in 2003 challenging the federal Partial-Birth Abortion Ban Act, and his case was argued before the U.S. Supreme Court three years later. In 2007, the high court upheld the ban on the procedure, which generally was used to end pregnancies in the second and third trimester. Doctors called it "intact dilation and extraction," or D&X, and opponents referred to it as partial-birth abortion. At the time of the Supreme Court's decision, Carhart said the ruling "opened the door to an all-out assault on" the 1973 ruling in Roe v. Wade.

The former Air Force surgeon also operates his own clinic, Abortion & Contraception Clinic of Nebraska, in a nondescript building in a working-class neighborhood of Bellevue, an Omaha suburb. But he said he doesn't perform abortions past the 22nd week of pregnancy there.

"Nebraska state law is based on viability. Nobody has defined that," he told the AP. "It's much cheaper to go build a new clinic in Kansas than to try to define what viability means in Nebraska."

The type of late-term abortions performed by Tiller, Carhart and the handful of others are rare. More than 820,000 abortions were performed in the United States in 2005, according to the most recent available data from the Centers for Disease Control. Less than 2 percent of abortions occur at 21 weeks of pregnancy or later, according to Guttmacher Institute, a reproductive-health think tank. It is unknown how many are done specifically in the third trimester, but Carhart said 75 to 100 of the "several thousand" abortions he performs annually are in the third trimester.

Abortion rights advocates also worry the group of physicians who can provide the service is dwindling.

"There are very, very few abortions that happen at that time," said Nancy Northrup, president of the Center for Reproductive Rights, who said she worries about a "severe shortage" of physicians who can perform the procedure. "People who need those services need caring and compassionate and qualified doctors like Dr. Tiller who are able to provide those services."

With Tiller's death, there are fewer than 10 doctors who perform third-trimester abortions in the United States, Carhart estimated, and though he has worked with younger physicians before, he hasn't trained any abortion providers in third-trimester techniques for at least five years.

Carhart, with his wife Mary by his side at a news conference Tuesday, said he'd be willing to train younger doctors but few want to put themselves or their families at risk.

"Young people starting families aren't going to want to go into abortion practice," Mary Carhart said. "If you were young with little kids, would you want abortion opponents outside your house?"

Another doctor who performs third-trimester abortions, 70-year-old Warren Hern of Boulder, Colo., said he's also concerned there won't be enough doctors trained to perform abortions in the future. Hern is an associate clinical professor at the University of Colorado-Denver School of Medicine, but he said he hasn't been asked to speak on the topic of abortion at the school in 21 years.

School spokeswoman Jacque Montgomery said full-time faculty mainly give lectures. As a clinical professor, she said Hern would teach students in the field, but she didn't know when Hern last worked with students.

Hern, who is being protected by U.S. Marshals following Tiller's killing, said many medical schools shy away from teaching about abortion and doctors don't want to learn about it.

"There are very few places that are teaching it," he said.

A day after Tiller was shot, Carhart vowed to reopen his friend's Kansas clinic and continue Tiller's mission. But on Tuesday, Tiller's family said there were no plans to reopen. Carhart said he remains hopeful that Tiller's family will change their minds. If not, he hopes another abortion provider will open a clinic in Kansas where he can work part-time.

For Carhart, the dispute over abortion is personal. In 1991, his family's rural home burned in a fire apparently started by an abortion foe.

But the Nebraska doctor said he's determined to continue doing what he does.

"As long as you have a terrorist who is willing to walk into a church and kill one person, as long as that element is in society, this is the risk we take," he said. "You can't live your life based on fear. You have to live by your principles."