The White House has said it was keeping to its policy on backing Israel's right to self defence following confirmation that Israeli tanks had punched across the Lebanese border and entered a strategic town.
"We are keeping to our adopted position. Israel has the right to defend herself," a White House spokesman said in response to the incursion.
"At the same time we urge restraint with regard to civilian life," the spokesman said by telephone.
Israeli General Beni Gantz said earlier that Israeli air and ground forces were almost finished taking over the strategic hill-top village of Marun Al-Ras, close to the Israeli border.
Lebanese security forces said that Israeli and Hezbollah forces were engaged in street battles in the village, where four Israeli soldiers and several Hezbollah militiamen were killed in battles in recent days.
The incursion came as US Secretary of State Condoleezza Rice prepared to fly on Sunday to the region to meet Israeli and Palestinian leaders in an attempt to find a way out of the Lebanese and Gaza Strip conflicts.
Washington has refused to bend to international pressure and call for a ceasefire. The fighting began July 12 following the abduction of two Israeli soldiers by the Hebollah militia.