SIMI VALLEY, California (CNN) -- President Bush on Friday urged the United Nations to quickly address the findings of its report implicating Syrian and Lebanese officials in the assassination of former Lebanese Prime Minister Rafik Hariri."Today, a serious report came out that requires the world to look at it very carefully and respond accordingly," he said. "The report is deeply disturbing."Bush said he instructed Secretary of State Condoleezza Rice to "call upon the United Nations to convene a session as quickly as possible to deal with this very serious matter." (Watch mixed reaction in Lebanon and Syria)Bush made his comments at the Ronald Reagan Presidential Library where he helped dedicate a new Air Force One exhibit.The United States is hoping to use the report to push Syria into ending its support for Palestinian militias and to stop allowing insurgents and fighters through its border into Iraq, CNN's Liz Neisloss reports."A report of that kind has got to be both discussed and debated in the U.N. Security Council, and there will have to be some way to ensure accountability for what has already been found here," Rice said. (Watch President Bush's reaction to the report)British Foreign Secretary Jack Straw -- in Birmingham, Alabama, with Rice -- said: "If we act swiftly and we act resolutely and we act together, then I believe the international community can show that it is standing up for justice."You simply cannot tolerate a situation where one state decides to deal with problems of another state by assassinating the other state's leaders."An administration source, who spoke on condition of anonymity, said Rice will ask for the United Nations to convene "early next week." The Security Council already is scheduled to meet Tuesday with the report's author, German prosecutor Detlev Mehlis.The Mehlis report concluded that there was "converging evidence" of Lebanese and Syrian involvement in the February 14 assassination of Hariri. (Full story)The report called on Damascus to "clarify a considerable part of the unresolved questions, saying "many leads point directly towards Syrian security officials as being involved with the assassination."The report said five senior officials -- including the brother and brother-in-law of Syrian President Bashar Al-Assad -- allegedly plotted to assassinate Hariri shortly after the United Nations called on Syria to remove its troops from Lebanon. Hariri was a key mover in getting the U.N. resolution passed.At a news conference Friday, Mehlis would not say if the Syrian government was cooperative during the investigation: "That's something we should leave for later."In his report, Mehlis concluded that given Syrian domination of its allied government in Lebanon "it would be difficult to envisage a scenario whereby such a complex assassination plot could have been carried out without their knowledge."The report found that Syrian authorities cooperated "to a limited degree" with the investigation, but several witnesses "tried to mislead the investigation by giving false or inaccurate statements."Fayssal Mekdad, the Syrian ambassador to the United Nations, told reporters the Syrian government "did not hinder the investigation," and he criticized investigators for focusing on "too much politics and less concrete actions.""At no point of the whole process did we mislead," he said. "It is not a credible report."Officials namedCNN was able to obtain a copy of the report given Thursday to U.N. Secretary-General Kofi Annan and Security Council members, which lists the names of the men accused of planning the February 14, 2005, bombing that killed Hariri and 22 other people.The names were not in copies of the report released for general distribution.In addition to Maher Assad, the Syrian president's brother, those investigating Hariri's death accused Assef Shawkat, the president's brother-in-law; Jamil al-Sayyed, head of Lebanese intelligence; Hassan Khalil, former head of Syrian intelligence; and Bahjat Suleyman, a personal friend of the Syrian president, as participating in planning the assassination.In an October 12 interview with CNN, the Syrian president denied reports -- recounted in Thursday's document -- that he had threatened Hariri. According to the report, Assad had demanded that the former premier support an extension of the term of Lebanon's president, Emile Lahoud, a staunch Syrian ally.The president told CNN that any Syrian involved in the plot "would be considered as a traitor and most severely punished."On Friday, Lahoud denied a claim in the report that he received a cell phone call from a suspect named in the report minutes before the bomb blast that killed Hariri.Lahoud's office, in a statement, called the allegation "baseless" and said it was "part of the continuing campaigns that target the presidency and the president himself and the national responsibilities which he holds and will continue to hold during this delicate time in Lebanon's history."The assassination sparked a wave of protests in Beirut that helped lead to Syria's announced withdrawal from the country in April.The U.N. probe concluded that the bomb used to kill Hariri was detonated above ground and used at least 1,000 kilograms (2,200 pounds) of military explosives. The convoy Hariri traveled in used jamming devices to prevent bombs from being detonated by remote control, so a suicide bomber may have set off the explosion.But investigators said further investigation was needed to determine how the bomb was set off.