Thousands of protesters are marching through Turkey's capital, urging parliament to reject a US request to use the country as a launch pad for an attack on Iraq.
Hundreds of riot police and several armoured cars blocked a main road leading to the parliament where deputies were set to debate a motion to allow U.S. troops into Turkey for a possible war.
More than 10,000 chanting and shouting protesters gathered in a central Ankara square, about a kilometre away, for a demonstration organised by trade unions. It was the first major public manifestation of widespread opposition to a war most Turks see as an unjustified and potentially disastrous attack on a neighbour.
"No to war, don't let people die," the crowd chanted in front of a stage where a large banner read, "The people will stop this war."
The government is under heavy pressure from NATO ally the United States to authorise some 62,000 U.S. troops to be deployed in Turkey to launch a "northern front" which experts say might shorten a war.
The ruling Justice and Development Party (AKP) has already deferred the parliamentary vote from Thursday amid widespread concerns about the impact of any war on Turkey's borders, further delaying U.S. military preparations.
AKP leader Tayyip Erdogan said he saw no prospect of the motion being withdrawn on Saturday.The resolution would also authorise Turkey's own army to move into northern Iraq for an incursion Turkey says aims to prevent a humanitarian disaster and block any moves by Iraqi Kurds to use a war to set up their own state.
Asked if he thought there was a possibility of the motion being withdrawn, Erdogan replied: "I don't see the possibility of anything like that. Nothing like that will happen."