It was the first time Syria, which has a 600 km desert border with Iraq, had reported cases of US troops firing on its forces.
The Foreign Ministry on Thursday told heads of diplomatic missions in Damascus in a letter that Syrian border troops had been subject to attacks "not only by infiltrators and smugglers but by the Iraqi and American forces".
"The border clashes amounted to about 100 armed clashes, some of which were carried out by American soldiers who opened fire arbitrarily at those present behind the dirt rampart due to loss of self control," said the ministry.
The US military in Iraq has launched several operations against anti-US fighters near the border in the past few months but has not reported any cross-border fire.
"The border clashes amounted to about 100 armed clashes, some of which were carried out by American soldiers who opened fire arbitrarily"
Syrian Foreign Ministry letter
In Washington, US officials at the Pentagon said they were unaware of any shooting incidents involving Syria but were checking with US forces in Iraq.
US officials accuse Syria of not doing enough to stop the fighters from crossing into Iraq to fight US and Iraqi forces and often say that they are using Syria as a conduit for the transfer of funds to fuel the armed opposition.
"Syria ... needs to take steps to go after those ... elements that may be operating on their territory and they need to play a helpful role with their neighbours," said White House spokesman Scott McClellan.
"Syria has been out of step with the rest of the Middle East. The Middle East has been leaning more and more in the direction of freedom and democracy," said McClellan.
Damascus said it was doing its utmost to seal its border with Iraq and stop it from being crossed by Syrian and other foreign fighters. Syria had prevented 1240 suspects from crossing into Iraq and extradited most of them to their respective countries, said the ministry.
About 4000 Syrians "who left or attempted to leave to Iraq to fight there have been investigated", it said. The United States and Britain had failed to respond to Syrian requests for night vision and radar-based monitoring systems to prevent night infiltrations, said the letter, delivered to envoys by Deputy Foreign Minister Waleed al-Mualem.
Syria said daytime infiltrations were now "a very difficult issue (for fighters) but the problem of infiltrations still persists to a certain extent during the night because of the lack of necessary technical equipment to monitor the border".
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It said Iraq had so far failed to ratify a protocol for security cooperation signed in Damascus in July 2004 and subsequent agreements.
Stability in Iraq was in the interest of Syria because it paved the way for the end of the presence of US led forces in Iraq, said the letter.