Egeland told a press conference on Thursday that a ceasefire in the five-week-old conflict between Israel and the Lebanon-based fighters would pave the way for a major aid operation for the "besieged populations of southern Lebanon".
"It's a disgrace really, because the parties to the conflict, the Hizbollah and the Israelis, could give us access in a heartbeat, and then we could help 120,000 people in southern Lebanon," he told a news conference in Geneva.
"I don't think any military advantage has been gained in these last days or will be gained in the next hours but we could save a lot of lives," he said.
Those in the south in need of assistance include 20,000 in the coastal town of Tyre, who he said were in increasingly desperate need after being cut off for days.
Egeland said Israel's bombing of bridges and roads in Lebanon, and its virtual "blanket denial" of authorisation for aid convoys there, had severely hampered UN humanitarian efforts.
"At the same time of course, the rain of missiles into Israel (by Hizbollah) has gone on unabated and this spreads a sense of terror which northern Israel has not seen since the creation of the state of Israel," he said.
He said civilians were the "big losers" in the conflict, which has claimed 1,011 lives in Lebanon and 121 in Israel.
"We hope and pray that the Security Council belatedly will be able to reach a... resolution to end it today [Thursday]," Egeland said.
"I don't think any military advantage has been gained in these last days or will be gained in the next hours, but we could save a lot of lives"
Jan Egeland, UN emergency relief coordinator
"That would be, as we see it, one month too late, but it would mean a dramatic turn if hostilities stop because we're on standby to immediately go with a major operation into the south and to help all of the civilian populations that are today besieged," he added.
Fuel especially is running desperately short in Lebanon, he said, adding that four hospitals in the south had run out and were unable to use generators vital for providing treatment.
"The national electricity grid will even halt if there is no fuel coming in soon," he said.