WASHINGTON — An abortion rights group has found that doctors and clinics in six states, including Missouri, that perform abortions "are routinely targeted" for legal and physical harassment, including death threats.

The result, according to a study by the Center for Reproductive Rights — an international legal advocacy group — is that women seeking to terminate pregnancies face a dwindling supply of providers as threats and intimidation take their toll.

Nancy Northup, the center's president, said physicians and clinics providing abortions have fallen by 25 percent since the 1990s.

Missouri has three, two operated by Planned Parenthood and one by a private physician who the center noted was approaching age 70.

"If any of the three clinics were to stop providing abortions, the harm would be devastating for women," according to the report.

Mary Kay Culp, executive director of Kansans for Life, which opposes abortion, said she hadn't seen the report. But she said the timing seems linked to the debate over whether federal funds should be used to pay for abortions under proposed health care reform bills.

"I can't help but think it's nothing more than an attempt to scare the American people away from being informed and concerned about the massive abortion mandates that are in the proposed health care reform bills," Culp said, "and that will remain there unless explicitly excluded."

Some states, such as Mississippi and North Dakota, also covered in the report, have only one abortion provider. Alabama has seven, while Texas has about 40 and Pennsylvania has about a dozen.

Most clinics are clustered in urban areas, leaving women in less populous regions to travel long distances for the service.

In 1992, Kansas — which was not included in the report — had 15 abortion providers; by 2005, that number had declined to seven.

The center concluded the study before the murder in May of physician George Tiller, who ran an abortion clinic in Wichita. His family closed the clinic after his death. The nearest clinic to Wichita is in Overland Park.

"Dr. Tiller's murder focused attention on this problem for a moment, but people don't realize that abortion providers operate under siege, legal and physical, every single day," Northup said.

Anti-abortion protests have become regular occurrences outside abortion clinics. Some physicians wear bulletproof vests, try to shield their home addresses from public records and take other steps to protect their privacy and safety, Northup said.

The report recommended that the Justice Department devote more resources to the problems that abortion clinics face. It also suggested better cooperation among state, local and federal law enforcement.

In addition, the center called on the medical community to take steps to increase the number of abortion providers and urged it to take a public stand against clinic violence and the harassment of medical personnel.

Abortion became legal in 1973 as a result of the landmark U.S. Supreme Court ruling in Roe v. Wade. About a third of all women will have the procedure during their reproductive years, the report claims.

The group singled out six states because it said they represented different parts of the country and were illustrative of the problems that abortion providers have experienced.