Hezbollah said the US 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 US-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 practicing terrorism while accusing others of it. The problem in Lebanon is US and Israeli interference."