DURHAM, N.C. (AP) — Durham County has become the first county in North Carolina to provide health insurance benefits to same-sex domestic partners of its employees.

Opponents have vowed to sue the county over the decision, however.

The unanimous vote by county commissioners, which received a long round of applause from supporters, caps about 10 months of debate on whether to offer the benefits. The issue surfaced after the city of Durham offered the coverage last year.

The city’s benefits are provided to employees’ unmarried heterosexual, as well as same-sex, partners.

Beginning next month, gay and lesbian county employees can enroll their partners and their children, with coverage starting Jan. 1.

“We are thrilled it passed unanimously,” said Nancy Blood, a longtime county librarian and spokesperson for the group lobbying for the benefits.

“We are sorry they didn’t do it for unmarried couples as well, but the commissioners were trying to do what they thought was the right thing.”

Couples must sign affidavits that a committed relationship has existed for at least six months and provide three documents that prove shared financial responsibilities. Accepted records include a joint bank account, a joint mortgage or lease, a health care agreement or an estate agreement.

The employee will have a month to notify the county if the relationship ends. The employee then will have to wait at least one year before enrolling another domestic partner.

Activist and City Council candidate Victoria Peterson vowed to sue the county because of the vote.

A group she helped organize, Christians for Morality in Government, has been raising money for the lawsuit since the city’s decision, but its members were waiting to see how the county would proceed, Peterson said.

Peterson also criticized holding the vote on a workday morning, saying that many who oppose the benefits couldn’t be at the meeting or weren’t aware of the vote.

“This issue should have been brought to a regular Monday night meeting so people in the community could come up and speak,” Peterson said. “I just feel it is wrong how the county commissioners have handled this, trying to bring this through the back door.”

Peterson tried to speak just before the vote, but Commission Chair Ellen Reckhow ruled her out of order. Citizens have to sign up two weeks in advance to speak at a morning work session.

The commissioners have argued that it is acceptable to offer the benefits only to same-sex couples because heterosexual couples have the option of marriage.

Their decision also is in line with County Attorney Chuck Kitchen’s earlier opinion that providing benefits to unmarried heterosexual couples would violate the County Commissioners’ oath of office. Kitchen has said that an 1805 statute outlawing cohabitation in North Carolina is a legal impediment to providing coverage for opposite-sex partners.

Besides Durham, the towns of Chapel Hill and Carrboro also offer domestic-partner benefits to straight and gay couples. City employees in Charlotte requested the coverage this spring.