Syria (search) challenged Washington on Wednesday to provide evidence of its claims that Damascus (search) has failed to stop anti-American militants from sneaking into Iraq, rejecting accusations of lax border control.

On Tuesday, President Bush said he was trying to gather allies in a diplomatic effort to stop Syria from blocking the emergence of democracy in the Middle East.

A day earlier, the U.S. ambassador to Iraq, Zalmay Khalilzad, said Washington was running out of patience with Syria's continuing role in Iraq's violence. Iraqi Foreign Minister Hoshyar Zebari on Monday also warned that Syria was playing a "dangerous game" in allowing insurgents to penetrate Iraq.

"This U.S. intimidation campaign proves that the Bush administration is searching for a scapegoat and for anyone to hold responsible for the failure of its foreign policies," Syrian state-run Tishrin newspaper said in an editorial Wednesday.

It said Washington was "incapable of providing even one piece of actual evidence that could prove its claims and lies because it simply has no evidence."

Bush said in a Tuesday news conference that Syria could "do a lot more to prevent the flow of foreign fighters into Iraq," and that Syria is "going to become more and more isolated" as a result of its policies toward Iraq and Lebanon (search).

"The Syrian leader must understand we take his lack of action seriously," Bush said.

In its editorial, the Syrian newspaper called Bush's statement "unjustified escalation of the media and political pressures on Syria" in reaction to two issues: The first, it claimed, was the crisis in Iraq; the second was U.S. annoyance over Syria's success in dealing with a U.N. investigation into the assassination of former Lebanese Prime Minister Rafik Hariri.

The United States has suggested that Syria played a role in the massive bombing that killed Hariri and 20 others in Beirut on Feb. 14. Syria has denied any role.

The chief U.N. investigator, Detlev Mehlis, came to Damascus on Monday at Syria's invitation and was expected to visit again next week after agreement was reached on arrangements for meeting with "Syrian witnesses."

The newspaper also said that the Bush administration had ignored "all significant measures" taken by Syria to control its frontier with Iraq, such as sending thousands of border troops.

Iraq and the United States both have complained that Syria has done too little to block the flow of insurgents into Iraq across the long and porous border. Syria has consistently denied allowing foreign fighters to cross, saying it is impossible to control the more-than-360-mile desert border.

On Sunday, Iraq closed a northern crossing point on the Syrian-Iraqi border in what Iraqi officials said was an attempt to halt the flow of insurgents.