Worried about antagonizing Turkish leaders, House members from both parties have begun to withdraw their support from a resolution supported by the Democratic leadership that would condemn as genocide the mass killings of Armenians nearly a century ago.

Almost a dozen lawmakers had shifted against the measure over the last 24 hours, accelerating a sudden exodus that has cast deep doubt over the measure’s prospects. Some representatives made clear that they were heeding warnings from the White House, which has called the measure dangerously provocative, and from the Turkish government, which has said House passage would prompt Turkey to reconsider its ties to the United States, including logistical support for the Iraq war.

Until today, the resolution appeared to be on a path to House passage, with strong support from the House speaker, Nancy Pelosi of California. It was approved last week by the House Foreign Affairs Committee. But this evening, a group of group of senior House Democrats had made it known they were planning to ask the leadership to drop plans for a vote on the measure.