US to debate Turkey genocide bill
A key US congressional committee is to debate whether to classify as genocide the deaths of 1.5 million Ottoman Armenians between 1915 and 1917
Turkey - which strongly denies Armenian claims that the killings amounted to genocide - has warned of "serious consequences" if the bill is passed.
Ankara has threatened to restrict US access to a key military base used for its operations in Iraq.
Arms deals between the two countries could also be cancelled.
The bill must pass in the foreign affairs committee before it can be debated on the floor of the House of Representatives.
Even if it passes and is then adopted by the House, the bill would not be binding.
Mood hardening
But the BBC's Sarah Rainsford, in Istanbul, says such a nuance will have little impact on the reaction in Turkey.
Ankara has pulled out all the stops to prevent the genocide resolution reaching Congress for a vote, she adds.
Politicians have travelled to Washington to lobby lawmakers, while the country's prime minister and president have both contacted US President George W Bush.
In his letter, Turkish President Abdullah Gul "drew attention to the serious problems that will emerge in bilateral relations if the bill is adopted," his office said in a statement.
An official government statement warned of the possibility of demonstrations and "other manifestations of anti-Americanism throughout Turkey" if the bill is passed.
Turkish political analyst Iltier Turan said the government in Ankara could feel obliged to act if the bill is approved.
"Any Turkish government will be compelled to demonstrate very concretely to the Turkish public that the Americans' unfriendly gestures are countered by equally unfriendly and punitive gestures on the part of Turkey," he said.
All this comes on top of mounting anger that the US is not doing enough to counter the Kurdish separatist PKK, which mounts deadly attacks on Turkey from inside Iraq, our correspondent says.
Long campaign
Ankara rejects Armenian claims that the deaths of some 1.5 million Armenians from 1915-17 amounted to genocide.
Turkey admits that many Armenians were killed, but says the deaths were a result of widespread wartime fighting in Turkey during World War I.
Armenians have long campaigned for the killings to be recognised internationally as genocide. Some countries have done so.
Last year Turkey cut military co-operation with France after the French parliament passed a bill to make denial of the Armenian genocide an offence - even though it never became law.
If the US bill is approved, Democratic Speaker Nancy Pelosi may allow a vote on the floor.
However, it would have no binding effect on US foreign policy, and similar bills in 2000 and 2005 were blocked by senior US politicians.
