Fighting on the Lebanon-Israeli border intensified after an Israeli air raid killed up to four UN observers and some 20 soldiers were wounded on Wednesday in fighting Hezbollah forces in the border town of Bint Jbeil.
In Rome, far from the region's smoke, bloodshed and rubble under which scores of civilians are reported to be buried or trapped, an international conference failed to agree on a call for an immediate ceasefire.
It vowed only to work immediately with "utmost urgency" towards one.
A declaration followed the US line, backed by Britain, that a ceasefire in the region "must be lasting, permanent and sustainable."
Arab countries had been calling for an immediate halt to hostilities.
Israel's two-week-old offensive in Lebanon has killed more than 400 people, mostly civilians, while its thrust into Palestinian territories has left 128 dead, including 12 killed on Wednesday.
In both cases the Jewish state is trying to recover a total of three soldiers captured by militants and halt rocket attacks on its territory.
In south Lebanon, the military met fierce resistance from the Shia militant group Hezbollah, which in turn is firing rockets on northern Israel.
"Around 20 soldiers were wounded in the fighting in Bint Jbeil," an Israeli spokeswoman said, referring to a key town in south Lebanon. Her statement followed a report on Israeli army radio that 13 soldiers were "hit" in heavy fighting there.
The Arabic news channel Al-Jazeera said 13 soldiers were killed and 12 wounded.