Obama said as a candidate that he believed the killings were genocide. A congressional resolution to that effect could alienate Turkey, a NATO ally and traditional friend of the United States that is crucial to US foreign policy goals.

Past US administrations have defeated similar resolutions through public cajoling about US national security interests and behind-the-scenes lobbying.

So far, however, the Obama administration has taken no public position on the measure. Aides to senior Democratic and Republican lawmakers on the House of Representatives Foreign Affairs Committee say there has been no pressure against the resolution from the White House. The administration was informed ahead of time that the committee would be scheduling the vote, according to Lynn Weil, spokeswoman for the committee's chairman, Democratic Rep. Howard Berman.

Ankara has long made clear that the issue could alter dramatically Turkish relations with the United States.

In 2007, when the House Armed Services Committee passed such a resolution, Turkey promptly recalled its ambassador, and US officials feared the Turks might cut off American access to a Turkish air base essential to operations in Iraq. After intensive lobbying by top Bush administration officials, the resolution was not considered by the full House.

Berman's committee is set to consider the issue Thursday.

A positive vote would clear the resolution to be considered by the full House. House Speaker Nancy Pelosi has said she will wait to see the result in the committee before deciding whether to bring it up for vote.

The United States still wants Turkey's support for its operations in Iraq and Afghanistan. It also is pressing Turkey, which holds a rotating seat in the UN Security Council, to support sanctions against Iran, Turkey's neighbor.

It is not known whether the committee will approve the resolution. The panel is strongly pro-Israel, and prospects for passage could be affected by rising tensions between Turkey and Israel, as well as Turkey's relatively warm relationship with Iran. In the past, Turkey and Israel had friendlier relations and Israel had quietly lobbied against the resolution.

Armenian American groups have sought for decades congressional affirmation of the killings as genocide.

Historians estimate that up to 1.5 million Armenians were killed by Ottoman Turks around the time of World War I, an event widely viewed by scholars as the first genocide of the 20th century. Turkey denies that the deaths constituted genocide, saying the toll has been inflated and those killed were victims of civil war and unrest.

This year, some Armenian groups and lawmakers are expressing optimism on the resolution's prospects, noting that Obama, Vice President Joe Biden and Secretary of State Hillary Rodham Clinton all supported recognition when they served in the Senate.

Democratic Rep. Adam Schiff, who introduced the resolution for consideration, said he sees more favorable conditions than in 2007.

"Last time we had President Bush calling lawmakers at their homes to oppose the resolution," he said.

In April, Obama broke a campaign promise to brand the killings genocide in an annual White House statement on the day marking Armenian remembrance. Obama said that while he had not changed his personal views, he did not want to upset promising talks between Turkey and Armenia on improving relations and opening their border. Turkey sealed the border in 1993 to protest Armenia's war with neighboring Azerbaijan.

In October, Turkey and Armenia signed an agreement to normalize relations, but Turkey has yet to ratify it. As progress toward a breakthrough between the two countries appears stalled, it may be harder for the Obama administration to oppose the resolution or refrain from calling the killings genocide in this year's statement.

"Our interest remains the achievement of a full, frank and just acknowledgment of the facts," said White House spokesman Mike Hammer, when asked about the resolution.

"We continue to believe that the best way to advance that goal is for the Armenian and Turkish people to address the facts of the past as a part of their ongoing efforts to normalize relations."

Hammer would not elaborate on the administration's position on the resolution.

Turkey's ambassador to Washington, Namik Tan, said the Turkish public may view the administration's silence on the resolution as pressure to ratify the agreement with Armenia.

"This could definitely complicate the process," he said.

"The greatest lobbyist in Washington is the administration. We have not seen them around enough on this."