(BBC) -President George W Bush has urged US legislators not to pass a resolution declaring the killing of Armenians by Ottoman Turks to be genocide.
"This resolution is not the right response to these historic mass killings," he said hours before a vote by the House Foreign Affairs Committee.
Such a move, already taken by France's parliament, would do "great harm" to US relations with Turkey, Mr Bush added.
Turkey admits many Armenians died in WWI but denies any genocidal campaign.
It is highly unusual for the White House to make such a dramatic last-minute intervention in Congressional business, the BBC's Justin Webb reports from Washington.
With the opposition Democrats now in charge in Congress, they could force a vote, dealing a potentially grave blow to the Bush administration's efforts to keep Turkey on side, our correspondent adds.