Israel on Saturday rejected a request by the United Nations for a three-day ceasefire in Lebanon to get in supplies and allow civilians to leave the war zone.
Avi Pazner, a government spokesman, said Israel already has opened safe corridors across Lebanon for such shipments and that Hezbollah guerrillas were blocking them to create a humanitarian crisis.
"There is no need for a temporary, 72-hour cease-fire because Israel has opened humanitarian corridors to and from Lebanon," he told reporters.
"The problem is completely different. It is Hezbollah who is deliberately preventing the transfer of medical aid and of food to the population of southern Lebanon in order to create a humanitarian crisis, which they want to blame Israel for."
Jan Egeland, the UN humanitarian chief, on Friday called for a three-day truce between Israel and Hezbollah to evacuate trapped civilians and replenish supplies to areas cut off by the fighting.
He said thousands of children, elderly and disabled had been stranded after more than two weeks of fighting, while supplies of food and medicines were dwindling.
Meanwhile, relief aid continued to arrive by air and sea on Saturday.
A US Navy high-speed HSV-2 catamaran arrived at the Beirut port from Cyprus bringing 20,000 blankets, 1,000 tarpaulins, large medical kits and other materials for immediate distribution, said Cassandra Nelson, a spokeswoman for the international aid organisation Mercy Corp.
She said the materials will be sent to the mountainous Chouf area east of Beirut, where the group has assisted refugees.
More aid was expected to arrive later and the group hopes to send it to southern Lebanon, she said.
Egyptian and Jordanian military transport planes also arrived at Beirut's airport with medicine, food and medical teams, while a third plane brought 40 tons of food and medical supplies from the United Arab Emirates.
At least 445 Lebanese, most of them civilians, have been killed in the offensive which began after Hezbollah kidnapped two Israeli soldiers and killed three others in a cross-border raid on July 12.
Thirty-three Israeli soldiers have died in fighting, and Hezbollah rocket attacks on northern Israel have killed 19 civilians, the Israeli army said.
Thousands of foreigners already have been evacuated from Lebanon by countries such as the United States, France and Britain, using planes and ships.