Turkey warned on Thursday that relations with its NATO ally the United States would be harmed by a U.S. House committee's approval of a resolution calling the 1915 massacres of Armenians by Ottoman Turks genocide.
The move came as Turkish Prime Minister Tayyip Erdogan prepared to ask parliament, which his party controls, to authorize a military incursion into northern Iraq to fight Kurdish Turkish rebels using the region as a base.
"The committee's approval of this resolution was an irresponsible move, which at a greatly sensitive time will make relations with a friend and ally, and a strategic partnership nurtured over generations, more difficult," the centre-right government said in a statement.
"Our government regrets and condemns this decision. It is unacceptable that the Turkish nation has been accused of something that never happened in history," the government said.
Turkey, which has NATO's second biggest army and plays a key role in a volatile region, has warned of damage to bilateral ties and military cooperation if Congress passes the measure.
The House of Representatives Foreign Affairs committee approved the resolution on Wednesday and it now goes to the House floor, where Democratic leaders say there will be a vote by mid-November.
Turkey said it would do all it could to stop the resolution being approved by the assembly.
Ankara rejects the Armenian position, backed by many Western historians and some foreign parliaments, that up to 1.5 million Armenians suffered genocide at the hands of Ottoman Turks during World War One.
Turkey says many Muslim Turks died alongside Christian Armenians in inter-ethnic conflict as the Ottoman Empire collapsed.
The White House had warned the resolution would harm ties with Turkey, which is an important logistics player in the Iraq war.
The bulk of supplies for troops in Iraq pass through Turkey's Incirlik airbase, and Turkey provides thousands of truck drivers and other workers for U.S. operations in Iraq. Supplies also flow from the base to troops in Afghanistan.
Diplomats say the committee's approval of the genocide resolution will weaken U.S. influence over Turkey at a time when the ruling AK Party ponders whether to authorize a major military cross-border operation into northern Iraq.
A large incursion would strain ties with the United States and the European Union, which Ankara hopes to join, and could destabilize Iraq's most peaceful area and potentially the wider region.
But Erdogan is under great pressure to act after rebel attacks have killed some 30 soldiers and civilians in the past two weeks.
He said late on Wednesday that his government could send the request to parliament on Thursday and obtain an approval after a holiday, which begins on Friday, to mark the end of the Muslim holy month of Ramadan.
Parliament, where Erdogan's AK Party has a big majority, would have to give permission for troops in big numbers to cross the border into neighboring Iraq. Passing the measure would not automatically mean Turkish troops going into northern Iraq.
Ankara blames rebels of the outlawed Kurdistan Workers Party (PKK) for the deaths of more than 30,000 people since the group launched its armed struggle for an ethnic homeland in southeast Turkey in 1984.
Turkey says U.S. and Iraqi authorities have so far failed to crack down on 3,000 PKK rebels believed based in northern Iraq, from where they stage attacks in Turkey.
Large-scale incursions by Turkey in 1995 and 1997, involving an estimated 35,000 and 50,000 troops respectively, failed to dislodge the rebels.
(Additional reporting by Evren Mesci in Ankara and Emma Ross-Thomas in Istanbul)