(Adds Syrian minister, Hezbollah comments) By Khaled Yacoub Oweis DAMASCUS, Nov 2 (Reuters) - Syria and Iran on Thursday dismissed a U.S. accusation that they are trying to topple Lebanon's government with their Lebanese ally Hezbollah. Hezbollah said the U.S. backing of the government of Prime Minister Fouad Siniora was "a blatant interference" in Lebanon's internal affairs and vowed to pursue its demand for a national unity government. "This pure vilification is meant to raise turmoil in Lebanon and cause fallout with Syria, which paid with blood to maintain Lebanese independence and sovereignty," an editorial in Syria's government newspaper Baath said. The White House said on Wednesday Washington had evidence that Syria, Iran and their allies in the Shi'ite Muslim group were preparing to topple the Beirut government, which is dominated by U.S.-backed politicians. The comments came a day after Hezbollah leader Sayyed Hassan Nasrallah gave Siniora and his majority allies until the middle of this month to agree on the formation of a unity government or face protests demanding a new election. "We do not care about such accusations. They're worthless," Syrian Expatriates Minister Buthaina Shaaban told reporters. "They are practising terrorism while accusing others of it. The problem in Lebanon is U.S. and Israeli interference." The Syrian newspaper said the United States should make public any evidence of the alleged Syrian role in efforts to topple the Lebanese government. U.S. officials say the information is classified. Iran's Foreign Ministry spokesman Mohammad Ali Hosseini denied the U.S. accusation and said Washington should review its policies in the Middle East. "These are repeated claims aimed to create divisions among Lebanese people and their government," Hosseini told Reuters. "HOLLOW SLOGAN" The United States has no diplomatic ties with Iran and has strained relations with Syria, accusing both countries of supporting terrorism and destabilising the Middle East. Both countries deny the charges. Iran says its offers only moral support to Hezbollah. A State Department spokesman said Nasrallah's ultimatum has raised U.S. concerns about the intentions of Hezbollah and other players towards Lebanon, which is still recovering from Israel's 34-day war with Hezbollah guerrillas in July and August. Anti-Syrian politicians had rejected calls for a national unity government, saying such demands were aimed at regaining Syria's influence in Lebanon. Hezbollah said the White House statement showed Washington's declared goal of promoting democracy in the Middle East was "a hollow and deceptive slogan". "We stress that this American violation of our national sovereignty will not terrorise our people or stop it from practising every one of its constitutional rights, led by the right to demonstrate, hold elections and chosing its government," a Hezbollah statement said. Lebanese Parliament Speaker Nabih Berri said Washington's strong support of Siniora's government could prove its undoing. Berri, a Shi'ite Muslim leader allied to Hezbollah, has called for roundtable talks between Lebanese leaders next week to discuss the formation of a new government. Syrian forces pulled out of Lebanon after a 29-year presence following last year's assassination of former Prime Minister Rafik al-Hariri. A U.N. investigation implicated Syrian security officials in the killing. Damascus, which denies involvement, has deepened its ties with Tehran after facing increasing isolation by the West following the assassination. (Additional reporting by Nadim Ladki in Beirut and Parisa Hafezi in Tehran)
