WASHINGTON (CNN) -- A U.S. delegation directly confronted Syrian President Bashar Assad -- on the third anniversary of 9/11 -- with evidence that Syrians were aiding militants crossing the border to foment deadly violence in Iraq, a senior U.S. government official has told CNN. President Bush had warned Syria before about its failure to police its borders, but the meeting with Assad -- as opposed to lower-level Syrian officials -- sent a more dire message, according to CNN Military Intelligence Analyst Ken Robinson, quoting the official. Robinson said the official did not describe what kind of evidence the U.S. presented...