Obama planned to announce his decision Wednesday in the Oval Office, the official said. The official spoke on the condition of anonymity because Obama had not signed a presidential memorandum putting his plan into place.
The decision is a political nod to a reliably Democratic voting bloc that has become impatient with the White House in recent weeks.
Several powerful gay fundraisers withdrew their support from a Democratic National Committee event June 25 where Vice President Joe Biden is expected to speak. Their exit came in response to a Justice Department brief last week that defended the Defense of Marriage Act, a prime target for gay and lesbian criticism.
Gays and lesbians also fretted as the White House declined to intervene in the cases of enlisted military members facing courts-martial for defying the Clinton-era "don't ask, don't tell" policies. Gays and lesbians can serve in the military now if they do not disclose their sexuality or engage in homosexual behavior.
White House officials say they want Congress to repeal the policy as part of a "lasting and durable" solution, instead of intervening on individual cases.
"The president agreed that ... the policy wasn't working for our national interests, that he committed to change that policy, that he's working with the secretary of defense and the joint chiefs on making that happen," White House spokesman Robert Gibbs said last month.
The administration has tried to make small, quiet moves to extend benefits to gays and lesbians. The State Department has promised to give partners of gay and lesbian diplomats many benefits, such as diplomatic passports and language training.
But Secretary of State Hillary Rodham Clinton's promises left out financial benefits such as pensions.
Obama's move Wednesday would direct the State Department to take into account same-sex couples and their children when assigning housing for foreign service officers. Those same-sex partners also would be allowed access to medical facilities at diplomatic posts abroad - all end-runs around Congress' limit on benefits.
White House officials said Obama would respect existing laws, which block many benefits such as health care. But the decision would allow employees' domestic partners to be added to a government insurance program that pays for long-term conditions, such as Alzheimer's disease.
The memorandum also would allow employees to use sick leave to take care of domestic partners and their children.
Richard Socarides, a New York lawyer and former senior adviser on gay rights issues to President Bill Clinton, was taking a wait-and-see attitude on Obama's announcement.
"If it doesn't include health insurance, if he doesn't talk about the military and about the (Justice Department) brief, I think it will fall short," Socarides said in an e-mail late Tuesday. "Right now, people are looking for real action."
John Berry, head of the Office of Personnel Management and the highest-ranking gay official in the administration, told a gay rally last weekend that Obama planned to take action on benefits soon.
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