Annan condemned an Israeli airstrike that killed at least 56 people in Lebanon early Sunday, telling an emergency council meeting that it must demand an end to the violence.
He said the region was becoming impatient that the council, the most powerful U.N. body, had yet to issue a meaningful response after three weeks of war in Lebanon.
"We meet at a moment of extreme gravity first and foremost for the people of the Middle East but also for the authority of this organization and especially this council," Annan said. "Action is needed now before many more children, women and men become casualties of a conflict over which they have no control."
The council been unable to take a stand on the fighting, partly because the United States, unlike other members of the council, has refused to back Annan's calls for an immediate cease-fire.
The Security Council's only response has been a weak statement expressing shock and distress at Israel's bombing of a U.N. post on the Lebanon border Tuesday that killed four unarmed military observers.
In unusually frank terms, Annan said the council risks undermining its own authority if it does not take action. He said that was underscored by attacks on the U.N. headquarters in Beirut Sunday, when protesters angry about the Qana attack smashed windows and hurled stones.
"People have noticed its failure to act firmly and quickly during this crisis," Annan said.
Lebanese special envoy Nouhad Mahoud echoed those complaints.
"Israel is committing atrocities against humanity," Mahoud said. The fact that the council has not taken up a resolution on civilian deaths, he said, "does not mean that the truth is to remain hidden."
The council met a day after a draft resolution was circulated among diplomats calling for an immediate halt to fighting between Israel and Hezbollah and seeking a wide new buffer zone in south Lebanon monitored by international forces and the Lebanese army.
It was unclear what the council would do later Sunday, although it could issue a statement condemning the Israeli attack.
The French-backed resolution is expected to be discussed in the coming days, and would almost certainly need changes before it is adopted. President Bush and British Prime Minister Tony Blair called Friday for a U.N. resolution that would lay the groundwork for peace in Lebanon and deploy an international force there.
Speaking before the council, Israeli Ambassador Dan Gillerman called it a "horrible, sad and bloody Sunday." While he apologized for the airstrike in Qana, he said there was no comparison between Hezbollah, which intentionally targets Israeli civilians and uses Lebanese civilians as human shields, and Israel, which tries to avoid civilian casualties.
"Those people including women and children who were killed in this horrible tragic incident may have been killed by Israeli fire but they are the victims of the Hezbollah," Gillerman said. "They are the victims of terror. If there were no Hezbollah this would never have happened."
Gillerman said Hezbollah must be disarmed before any cease-fire. Otherwise, he said, the militant group will rise again"not just against us and not just against the people of Lebanon, but against the whole region and civilization as we know it."
Syria's Ambassador Bashar Ja'afari was quick to fault the United States for the attack, saying it was carried out with "American bombs."
"They call them smart bombs, but actually they are silly bombs," he said. "They call them laser-guided bombs but (they) are actually hate- guided bombs."