Today the US House of Representatives' Foreign Affairs Committee will pass a resolution calling on President Bush "to accurately characterise the systematic and deliberate annihilation of 1.5 million Armenians as genocide".
The killings, whose scale and character are fiercely contested by Turkey, were carried out by Ottoman troops beginning in 1915. While Ankara is prepared to acknowledge a "tragedy" it insists that those who died on both sides of the bloody conflict were victims of war and it deeply resents an implied analogy with Nazi war crimes.
The Turkish government has been lobbying heavily to block the resolution which is sponsored by some 226 of 435 members of the house. In the past it has succeeded in getting such motions shelved by leaning heavily on administration concerns not to offend a most loyal strategic partner and member of Nato.
Similar resolutions were approved by the house in 1975 and 1984 but did not make it through the Senate. A 1990 resolution was blocked by a Senate filibuster. This time there have been calls from Prime Minister Tayip Erdogan to Bush, who has spoken out against the motion, and to Bill Clinton, urging him to use his influence among Democrats.
Erdogan has warned that the political fall-out could be long and lasting, fuelling nationalist anger and potentially jeopardising important links.
Dan Fried, the state department's top Europe official, warned last week it could "hurt our forces deployed in Iraq, which rely on passage through Turkey . . . We have to be mindful of how much we depend and how much our troops and the Iraqi economy depend on shipments from and through Turkey". Turkish diplomats argue the motion could stymie tentative moves towards a rapprochement between Turkey and Armenia. The latter is sceptical.
In terms of historical fact there is some case for the recognition of a monstrous injustice, although what purpose exactly is served by the diplomatic equivalent of a sharp poke in the eye is arguable.
What is more important to Turkey's friends in Europe, however, is the perception that the country remains unable still to debate this neuralgic issue domestically in a manner that respects democratic norms. Those writers and intellectuals who try to raise it face possible prosecution under the notorious Article 301 of its penal code that makes it a crime to insult Turkish national identity.
Despite a willingness last week at the Council of Europe from President Abdullah Gul to countenance Article 301's repeal, his AKP party has made it clear its priority is the debate on a new constitution. Unfortunately today's motion is likely to reinforce rather than change that prioritisation.