Syria accused the US yesterday of "terrorist aggression" after a raid near its border with Iraq in which it said eight civilians were killed but Washington refused to say whether its troops were involved.
Syria says four US helicopters attacked al-Sukkari farm on Sunday in the Albou Kamal area in eastern Syria and that US soldiers stormed a building there. Washington blames Damascus for failing to stem the flow of al Qaeda fighters and other insurgents from crossing into Iraq.
"The Americans do it in the daylight. This means it is not a mistake, it is by blunt determination. For that we consider this criminal and terrorist aggression," Syrian Foreign Minister Walid al-Moualem told a news conference in London.
The Iraqi government said the strike targeted insurgents who attack Iraq. Mr Moualem said Syria would ask the US and Iraq for an investigation into the attack.
"We put the responsibility on the American government and the need to investigate and return back to us with the result and explanation why they did it," Mr Moualem said.
Iraq's territories should not be used "to launch aggression against Syria", he said.
Washington has neither confirmed nor denied responsibility for Sunday's raid. If confirmed, it would be the first such US military strike inside Syria since the 2003 invasion of Iraq.
"I will say this once and you can ask me as many times as you want to: I have no comment on any alleged operation in Syria," Pentagon spokesman Bryan Whitman said.
White House spokesman Dana Perino also refused to comment on any questions relating to the reported incident in Syria.
"I am not able to comment on reports about this reported incident, and I'm not going to. I'm not going to do so, you can come up here and try to beat it out of me but I will not be commenting on this in any way, shape or form today, or tomorrow," she said.
Asked whether the Syrians would use force if the Americans conducted a similar raid in future, Mr Moualem said: "As long as you are saying if, I will tell you if they do it again... we will defend our territories".
Iraqi government spokesman Ali al-Dabbagh said the attack was launched against "terrorist groups operating from Syria against Iraq", including one which had killed 13 police recruits in an Iraqi border village.
"Iraq had asked Syria to hand over this group, which uses Syria as a base for its terrorist activities," Mr Dabbagh said.
He did not say who had carried out the raid.
A US general said last week that US and Iraqi security measures had reduced the flow of insurgents from Syria.
"The Iraqi security forces and the Iraqi intelligence forces feel that al Qaeda operatives and others operate, live pretty openly on the Syrian side," Marine Major General John Kelly, who commands US forces in western Iraq, told reporters.
"And periodically we know that they try to come across," he said, citing a May 2 raid that killed 11 Iraqi police. Syrian Interior Minister Bassam Abdel Majeed said last week that his country "refuses to be a launching pad for threats against Iraq".
US forces in western Iraq denied involvement. But the mayor of the Iraqi border town of Qaim said on Sunday that US helicopters had struck a village on the Syrian side.