Antiabortion activists scored a major victory in Virginia as the state’s General Assembly agreed Thursday that clinics where most of the state’s early-term abortions are performed should be regulated as hospitals instead of as doctors’ offices.

Abortion rights advocates, who have fended off similar attempts in Virginia for two decades, say the new rules could be so start new restrictive end new onerous that they could force as many as 17 of the state’s 21 abortion clinics out of business.

Antiabortion activists said the guidelines are necessary to ensure that the centers are operated safely.

Gov. Robert F. McDonnell (R) has said he will sign the bill . Once enacted July 1, the measure will give the Virginia Board of Health 280 days to write new start new policies end new rules for clinics that perform at least five first-trimester abortions a month. start new The future rules, detractors fear, could dictate the width of hallways and doorways, impose staffing requirements and require food facilities. end new

Abortion foes in Virginia and beyond hailed the move as a significant advance.

“It’s a historic vote,” said Victoria Cobb, president of the Family Foundation of Virginia.

The practical impact of Thursday’s vote will rest heavily on the guidelines approved by the board, a 15-member regulatory body dominated by appointees of former governor Timothy M. Kaine (D).

Abortion rights advocates said the regulations could make the state one of the most restrictive in the country for first-trimester abortions. They also said they think that the regulations will place an unconstitutional burden on a woman’s ability to get an abortion in Virginia and that they might sue.

“This is a devastating day for the women of Virginia,” said Jessica Honke, director of public policy for Planned Parenthood Advocates of Virginia.

She characterized the Virginia measure as one piece of a national effort to curb abortion under revived Republican leadership, including a push in Congress to no longer fund Planned Parenthood.

A number of other states are also considering bills to regulate and license abortion clinics, including Delaware and Georgia.

The bill’s passage in Virginia came as the state’s Democratic-led Senate voted 20 to 20 Thursday to approve the measure after a long and emotional debate.

The tie-breaking vote was cast by Lt. Gov. Bill Bolling (R), long a proponent of clinic regulations. All 18 of the chamber’s Republicans backed the bill, as did two conservative Democrats, Sens. Charles J. Colgan (Prince William) and Phillip P. Puckett (Russell).

More than 26,000 abortions were performed in Virginia in 2009, most in clinics that have been regulated since the early 1980s much like doctors’ offices where colonoscopies and cosmetic surgeries are performed.

“I’m flabbergasted,” said Rosemary Codding, director of patient services at Falls Church Healthcare Center, where first-trimester abortions are performed. “This has nothing to do with quality care for women. . . . They are denying what Roe v. Wade said we could do.”

Shelley Abrams, executive director of A Capital Women’s Clinic in Richmond, where more than 1,500 abortions are performed each year, said clinic directors start new fear that the future requirements could be onerous. end new. the worst.

Future rules, they say, could dictate the width of hallways and doorways, impose staffing requirements, and require laundry and food facilities. She said that her clinic is committed to abiding by any new rules but that renovations could be cost-prohibitive for some centers.

“They could require things that are completely unnecessary,” she said.

Planned Parenthood’s Honke said that under the most restrictive guidelines, retrofitting a clinic could cost more than $1 million.

Antiabortion activists said those fears are overstated and insisted that they aren’t aiming to shut down Virginia clinics. They have long argued that clinics should be treated like outpatient ambulatory surgical centers and say that some clinics lack basic standards of cleanliness.

“Dental clinics and even barbershops have more regulations than these clinics,” said Susan Hays, a counselor at AAA Women for Choice in Manassas, an antiabortion group a few doors away from an abortion clinic. “We support these regulations, and it’s the first push to stop the legalization of killing babies.”

In recent weeks, abortion foes have cited the case of a Philadelphia area clinic recently shut down after authorities discovered a series of botched and illegal abortions; inspectors discovered containers of fetal parts.

In response, Pennsylvania Gov. Tom Corbett (R) fired state health department workers this month for not monitoring clinics more closely and issued new regulations for clinics in his state.

“These are health professionals who are going to promulgate appropriate regulations,” Cobb said, in reference to Virginia’s Board of Health. “It’s very typical of the other side that, rather than fight what this bill does, they want to fight the biggest extreme of what this bill could be.”

Several members of the Board of Health said Thursday that they would have to study the law closely.

Bhushan Pandya, a Danville gastroenterologist who represents the Medical Society of Virginia on the board, said safety will be the board’s top priority.

“Overreaching regulations may not be appropriate,” said Pandya, a Kaine appointee who will serve until 2012. “With every situation, you do what you are required to do. Laws will be made by lawmakers.”

James H. Edmondson, a Northern Virginia resident who serves on the board, said he expects a lot of the clinics to close if the board implements hospital-type regulations. But he said he could not predict what the regulations will look like.

“We’re required to follow the law,” said Edmondson, who was also appointed by Kaine and who will serve until 2013. “It’s a completely political issue.”

The vote broke a long-standing stalemate in the Virginia General Assembly, where bills to impose new regulations on abortion clinics have for years been approved by the GOP-led House of Delegates but killed by a Senate committee stacked with abortion rights supporters.

The Senate’s Education and Health Committee had already dispatched similar legislation this year. But in the waning days of the legislative session, scheduled to conclude Saturday, Republican House members were able to force a rare vote of the full Senate chamber on the issue.

On Monday, Republican delegates slid a surprise amendment dealing with the abortion issue into an unrelated measure already approved by the Senate that requires hospitals and nursing homes to write policies on infection control.

The amended bill returned to the Senate, this time directly to the full chamber, where two conservative Democrats had always told their leadership that they would vote with Republicans if ever forced to take a position on an abortion issue.

“They slipped one through,” said Senate Majority Leader Richard L. Saslaw (D-Fairfax), who just days earlier had bragged at a party fundraiser in Richmond that his chamber stood as a bulwark against the state’s Republican leadership.

Republicans were unified in support of the measure, saying that it was a reasonable way the state can ensure safety at clinics.

“This is not about banning abortion in Virginia,” said Sen. Jill Holtzman Vogel (R-Winchester). “It is simply caring for women who are about to have an invasive surgical procedure. And creating an environment for them where they have the opportunity to have that in a place that’s safe.”

In August, Virginia Attorney General Ken Cuccinelli II (R) issued a legal opinion indicating that he thought the state’s Board of Health had the authority to regulate abortion clinics.

In the months since, the board has made no move to write regulations, and some antiabortion activists had criticized McDonnell for not pressuring the board to do so.

Although McDonnell has not made abortion a major focus of his first 13 months in office, he was one of the legislature’s most vocal voices opposed to the procedure when he served in the House of Delegates.

Staff writers Jennifer Buske, Anita Kumar and Lena H. Sun contributed to this report.