UN chief Kofi Annan has made a strong plea to member states to provide troops for a peacekeeping force in Lebanon.
Lebanese troops have reached the southern border with Israel
A week after a UN ceasefire resolution was passed, Mr Annan said the situation on the ground was still "fragile".
He urged Israel immediately to lift its air and sea blockade on Lebanon so aid could be delivered quickly.
The ceasefire has largely held, but Lebanese military sources said Israel staged a raid in the Bekaa Valley on Saturday. Israel has not commented.
Reports on Hezbollah's TV station say Israeli commandos were flown into the area, some 100km (60 miles) north of the Israeli border, but were repulsed by Hezbollah fighters. Israeli missile strikes in the area were also reported.
If the reports are confirmed, they will constitute the first major incident between the two sides since the UN-brokered ceasefire came into effect on Monday.
As efforts continue to build a UN peace force, senior officials have urged Europe to pledge more troops.
UN TROOP PLEDGES
France - leadership and 200 troops
Bangladesh - two battalions (up to 2,000 troops)
Malaysia - one battalion (up to 1,000 troops)
Indonesia - one battalion, an engineering company
Nepal - one battalion
Denmark - at least two ships
Germany - maritime and border patrols
Sources: UN diplomats
Israel has said it may be "inconceivable" to accept nations that denied its right to exist, such as Malaysia and Indonesia, as part of the planned 15,000-strong force for south Lebanon.
While thanking Asian nations for their firm commitment, UN Deputy Secretary General Mark Malloch Brown said the force had to be "multilateral" in character.
Two senior UN envoys, Vijay Nambiar and Terje Roed-Larsen, have arrived in Beirut for talks on how the UN-brokered truce is being implemented.
When the UN Security Council agreed the ceasefire resolution last week, Mr Annan promised to report back on progress within seven days.
His update is cautiously positive, the BBC's Mike Sergeant reports from UN headquarters in New York.
Mr Annan says only a handful of violations of the ceasefire have been observed and he praises what he describes as "the constructive efforts" of both the Lebanese and Israeli armies in upholding their obligations.
But he warns that the overall situation remains "fragile" and he strongly appeals to member-states to provide emergency reinforcements for the UN peacekeeping operation.
The UN has been struggling to persuade Europeans to provide the bulk of an initial deployment of 3,500 troops to go in by 2 September, our correspondent says.
France has agreed to lead the force but its immediate pledge of only 200 extra troops is far smaller than expected.
French Defence Minister Michele Alliot-Marie has stressed that the troops must have clear rules of engagement.
Mr Malloch Brown said the expanded UN force in Lebanon would not be "offensive", nor would it be asked to "attempt large-scale disarmament".
"Rather it is going to police the political agreement which triggers disarmament called for under the resolution," he said.
Lebanese troops have reached the southern border with Israel - a vehicle carrying a Lebanese flag made a symbolic pass a few metres from the border at Kfar Kila.
The UN says 400,000 people have returned to homes in the south and in the heavily bombed southern suburbs of Beirut.
Lebanese President Emile Lahoud has praised what he called the victory of Hezbollah against Israel in a televised address to the nation.
He said he saluted Hezbollah leader Sheikh Hassan Nasrallah "who willed this victory to be a victory for all Lebanese and all the Arab peoples".
At his presidential retreat in Camp David, President George W Bush again condemned Hezbollah as a "force of instability".
"Sometimes it takes people awhile to come to the sober realisation of what forces create stability and what don't," he said.