Washington - The United States demanded the immediate withdrawal of Hezbollah fighters from Syria on Wednesday, saying their active role in combat there was an "extremely dangerous escalation".
Hezbollah leader Hassan Nasrallah confirmed last week that the Lebanon-based Shi’ite movement was actively fighting on the side of its close ally, Syria's President Bashar Assad, in the Syrian town of Qusayr near the border.
"This is an unacceptable and extremely dangerous escalation. We demand that Hezbollah withdraw its fighters from Syria immediately," State Department spokesperson Jen Psaki said.
Hezbollah fighters spearheaded an assault that cut off Syrian rebel fighters, drawing condemnation from the UN human rights body.
In Geneva, 36 of the 47 members of the UN Human Rights Council voted in favour of a resolution that implicitly refers to the involvement of Hezbollah fighters from neighbouring Lebanon in the fierce battle for Qusayr.
The non-binding text put forward by the United States, Turkey and Qatar "condemns the intervention of foreign combatants fighting on behalf of the Syrian regime in al-Qusayr".
Psaki also condemned the "outrageous attack" on a Lebanese army checkpoint near the border on Tuesday that killed three soldiers.
It was not immediately clear who was behind the attack, which was condemned by the Lebanese government and Hezbollah.
"These and other incidents are stark reminders that the conflict in Syria poses an incredibly dangerous threat to Lebanon's stability, the people of Lebanon and security," she said.
"We call on all parties to do their part to act with restraint and respect Lebanon's stability and security."
Hezbollah, which battled Israeli forces for nearly two decades before their 2000 withdrawal from Lebanon, had long insisted its arsenal of rockets and other weapons would only be used to defend Lebanon from its southern neighbour.
But Nasrallah has said the group must now defend Assad's regime against an uprising increasingly dominated by hard-line Sunni Islamists who view Shi’ites and Assad's offshoot Alawite sect as apostates.
Hezbollah in Syria
Hezbollah's involvement in Syria has raised fears the conflict could spill over into Lebanon, where deadly clashes between supporters and opponents of the Syrian regime have periodically erupted in the northern city of Tripoli.
Syria has long been a crucial conduit for arms supplied to Hezbollah by its chief patron Iran. Iran, Syria, Hezbollah and some Palestinian groups view themselves as an axis of "resistance" against Israel and the West.
Hezbollah is believed to have sent at least 1 700 fighters to Qusayr more than a week ago to support the regime's assault on the rebel stronghold. France estimates that 3 000 to 4 000 Hezbollah fighters are operating in Syria.
Hundreds of civilians have reportedly been killed in Qusayr and thousands could be trapped. The United Nations estimates that more than 70 000 people have been killed since the initially peaceful uprising began in March 2011.
The State Department noted progress on the diplomatic front for an international peace conference that would include representatives of the Syrian regime and the opposition. Iran's possible participation in the talks has not yet been decided.
"Iran has not played a constructive role in regard to Syria," Psaki said.
"They have sent weapons. They have sent money. They have provided fighters. They have financed Hezbollah. And we have no reason to believe that Iran wants a peaceful transition."
Tehran has indicated that it has obtained an oral invitation to participate in the conference, dubbed Geneva II.