A US attack on a convoy that was believed to have been carrying Iraqi leaders may have taken place inside neighbouring Syria, a Pentagon official has admitted.
US officials believe Saddam Hussein and his sons are still alive
At least five Syrian border guards were injured in the attack, which was carried out by US special forces backed by aircraft, US officials said.
US military spokesman Lieutenant Colonel Gary Keck said the US was working with the Syrian Government to determine precisely where the attack occurred.
There has been no official comment from Damascus but a spokesperson at the Syrian Foreign Ministry told BBC News Online that a statement would be released later on Tuesday.
Syria has been under intense pressure from America since the war in Iraq not to provide sanctuary to Saddam Hussein or any other Iraqi fugitives.
US special forces, backed by AC-130 gunships and helicopters, took part in the attack on the convoy near the western Iraqi city of Qaim, close to the Syrian border, five days ago.
An unmanned aircraft, or drone, was also involved in the operation.
There's a lot of intelligence out there that you don't know if it's true or not
US defence officials said a number of people had been killed in the attack.
Officials said 20 people in the convoy were arrested and questioned, but most were subsequently released.
Intelligence reports had apparently suggested that the convoy was carrying ousted Iraqi President Saddam Hussein and at least one of his sons, Uday and Qusay.
There has been widespread speculation that the attack was an attempt to kill Saddam Hussein.
But the Americans have said there is no evidence that he was among those killed.
It is unclear how the Syrian border guards came to be involved.
Investigations, including DNA testing, are reported to be taking place into the identities of the victims.
The search for Saddam Hussein has been led by Task Force 20, which specialises in covert actions and works closely with American intelligence agencies.
The search for the deposed leader has intensified since the recent capture of a close aide, Mahmud al-Tikriti, who has told US interrogators that Saddam Hussein and his sons are still alive.
However, US officials said they had not determined the truth of the statements.
US forces have previously attempted to target Saddam Hussein and his sons, including air strikes on locations in Baghdad where intelligence apparently indicated they might be on 20 March - the first night of the war - and 7 April.