U.N. officials say they asked Israel to stop shelling a military outpost in Lebanon hours before it was destroyed, killing four U.N. observers. Israel denies it deliberately targeted the post.

Photo released by United Nations Interim Force in Lebanon, shows U.N. observation post that was damaged after Israeli air strike, Tuesday

Senior U.N. officials say they contacted Israeli authorities more than 10 times to plead for a halt to the shelling of a U.N. observer post Tuesday, in the hours before the post was destroyed by Israeli shell fire. Four U.N. military observers were killed in the incident, one each from China, Austria, Finland and Canada.

One senior official, briefing reporters on background, said Deputy Secretary General Mark Malloch Brown and Assistant Secretary-General for Peacekeeping Jane Holl Lute telephoned Israel's ambassador to the United Nations several times to enlist his help in having the shelling stopped.

They said the ambassador, Dan Gillerman, expressed concern and assured them that the U.N. was not a target. A spokeswoman for the Israeli U.N. mission confirmed the account for VOA.

China Wednesday asked Israel to apologize for the attack. The Chinese U.N. Ambassador Wang Guangya said the incident was 'inexcusable'.

Wang Guangya talks to the press during Security Council consultations, Wednesday

"For China and for others, we condemn this,"the ambassador said. "Because I think any attack on the United Nations positions and United Nations personnel is inexcusable and unacceptable".

Secretary-General Kofi Annan initially issued a statement Wednesday calling the attack 'an apparently deliberate action'. He later told a news conference in Rome he had spoken to Israeli Prime Minister Ehud Olmert, who expressed 'deep sorrow' for the incident. He said Mr. Olmert 'definitely believes it was a mistake'. Israel's defense ministry described the incident as an accident.

Briefing a closed door Security Council meeting Wednesday, Assistant Secretary-General Lute described a virtual barrage of missile and artillery fire around the observer mission in the hours before the fatal strike. She displayed pictures of the outpost to show it was well marked as a U.N. facility, and said that unlike other areas, there had been no firing by Hezbollah units in the area.

China asked the Security Council Wednesday to issue a statement condemning the attack. But diplomats say the approval of the statement was bogged down in disputes over wording.

U.S. Ambassador to the U.N. John Bolton said Washington would object to any attempt to politicize the incident.

John Bolton talks to the press during Security Council consultations, Wednesday

"The objective of United States here is to make an appropriate statement in a very timely fashion about the deaths of the four UNIFIL observers and not to make this statement a backdoor way of getting into ceasefire or other larger political and military questions," he noted. "That's not appropriate here."

A White House spokesman Wednesday said Israel should be taken at its word that the air strike was an accident. The spokesman also said it is important to find out what went wrong and to ensure it never happens again.