TUSCALOOSA, Alabama (Reuters) - Secretary of State Condoleezza Rice demanded accountability on Friday after a U.N. report said high-ranking Syrian officials and their Lebanese allies were involved in the killing of former Lebanese Prime Minister Rafik al-Hariri. "Accountability is going to be very important for the international community," Rice told reporters as she flew with Britain's Foreign Secretary Jack Straw for a tour of Alabama. "We cannot have the specter of one state's apparatus having participated or having been involved in the assassination of the former prime minister ... in another state." Rice did not specify what action the United States wanted the United Nations Security Council to take against Syria. But her remarks intensified international pressure on President Bashar al-Assad, whose brother-in-law is suspected of being involved in the plot. The U.N. inquiry into the February 14 killing, led by veteran German prosecutor Detlev Mehlis, has established "that many leads point directly toward Syrian security officials as being involved with the assassination." Syria's ambassador to the United States dismissed the investigation as "gossip." But Rice said the findings were clear. "Even an initial reading of the report is deeply troubling," she said. "You have clearly a case in which there is an implication that Syrian officials were involved in the assassination of Rafik al-Hariri. You also have a clear indication that the Syrian government has not been cooperating." "These are charges that will lead the international community to have to seriously consider how it demand accountability," she added. The top U.S. diplomat said she was hammering out with her counterparts from countries on the U.N. Security Council, including Straw, on how to respond to the report, which has been submitted to the 15-nation council. Asked if that response would include pressuring Lebanon's President Emile Lahoud to resign after the report cast suspicion on him, Rice said she was still digesting the U.N. investigator's findings in a sign Washington would not target him. Straw said the report showed Syrian "arrogance" toward a small neighbor it considered its "fiefdom." The two officials said international diplomacy would focus on stopping any Syrian meddling in Lebanon to ensure the small nation's sovereignty. The United States, France and Britain have been discussing possible U.N. resolutions as a follow-up to the report, but no texts have been drafted, diplomats said. The U.S. reaction to the report is part of a campaign against Syria, which also includes Washington's accusations that Damascus does too little to stop insurgents entering Iraq and supports anti- Israel militant groups.