The Obama administration has all but officially recognized gay partnerships as the legal equivalent of marriage, gradually redefining the concept through a series of changes to regulations governing benefits for federal employees.

At least a dozen government-wide regulations issued in the past year expand spousal benefits — such as long-term care insurance and child care vouchers — to the same-sex partners of federal employees. The agency-level changes introduced for the first time the term “domestic partnership” into bureaucratic lexicon, carving out a special category for gay couples.

In June 2010, the president announced with fanfare that the agencies would extend all possible benefits to same-sex partners of employees. It was the first of several steps — including the repeal of “don’t ask, don’t tell” — that the administration has taken in response to growing pressure from the gay and lesbian community.

The 1996 Defense of Marriage Act defines marriages as a union of one man and one woman and prohibits the federal government from recognizing any other marriage.

That law still stands, preventing the extension of several key statutory benefits to gay partners — including health care for federal employees ­­— but the regulatory modifications provide an important symbolic step in the eyes of gay-rights advocates.

As the president’s 2012 re-election campaign moves into full swing, Obama was the scheduled headliner at Saturday night’s annual fundraiser of the Human Rights Campaign, one of the country’s largest gay-rights groups.

The speech capped off a week that brought two more of these incremental changes: The Pentagon announced Friday that military chaplains could perform same-sex unions, and the General Services Administration ruled on Wednesday that it would cover the moving costs for domestic partners of transferred federal employees.

“It’s things that people don’t think of often, but they are meaningful when couples get access,” said Brad Jacklin, who handles government affairs for federal agencies at the National Gay and Lesbian Task Force. “It’s a recognition that there are valued employees in the federal government who are living in same-sex households. The reality is the Obama administration has done what it can.”

The federal government now provides sick and emergency leave for all federal employees caring for gay partners and the children of those partners. Some agencies have also extended credit union membership, access to fitness facilities and financial, parenting and adoption counseling services to the gay partners of federal employees.

Twenty-two states and the District of Columbia already make similar benefits, including health care, available to public employees and their same-sex partners, and more than half of Fortune 500 companies have followed suit, according to data collected by the HRC.

The administration’s moves are “an example to the companies out there that don’t offer these benefits,” said Brian Moulton, chief legislative counsel at HRC. “Twenty-nine states don’t have a law prohibiting discrimination on the basis of sexual orientation. In a lot of these places, the federal government is the most progressive employer.”

The HRC led an aggressive lobbying campaign for the expanded benefits, winning its first victory in June 2009 when the State Department announced it would modify a series of provisions, such as emergency travel and overseas allowance, to include same-sex partners of individuals in the Foreign Service.

The organization has spent $5.3 million on lobbying the administration and Congress since Obama took office, about $1 million more than it spent by this point in second term of the Bush administration, according to federal records. During that time period, HRC employed six outside firms to augment the work of seven federally registered in-house lobbyists.

Obama has called for the repeal of DOMA, but the administration does not have the support of many Republican Members of Congress. As an alternative, he has endorsed legislation introduced by Rep. Tammy Baldwin (D-Wis.) and Sen. Joe Lieberman (I-Conn.) that would extend the Federal Employees Health Benefits Program, life insurance and pension program to gay couples.

Conservative outside groups object to the expansion of any benefits to gay couples, arguing that it violates DOMA.

“I consider this to be a violation of the spirit, if not the letter of the federal Defense of Marriage Act,” said Peter Sprigg, a senior fellow for policy studies at the Family Research Council who focuses on marriage issues. “It’s inappropriate for the executive branch to create this category that has no statutory basis. … They want an unlimited smorgasbord of relationship options whose only common denominator is that they are subsidized by the government.”

The term “domestic partner” was first defined in a June 2010 by the Office of Personnel Management as a “committed relationship, between two adults, of the same sex.” Domestic partners of the opposite sex who choose not to marry are not eligible.

“At first, we started dealing with opposite-sex [partners],” said Rodney Miller, who manages travel and relocation policy at the GSA. “[The Office of Management and Budget] said no. All they wanted us to do was address the executive order. They are manning the budget of all the federal government, so they knew this is going to cost a few dollars to extend it beyond that.”

White House officials were unable to provide a dollar figure for what it will cost the government to extend benefits such as travel and relocation assistance to gay couples; however, one source at OPM said “our expectation is that the costs are negligible.”