BAGHDAD, Aug 22: The debate over responsibility for the breach of security that enabled the devastating bombing of the United Nations’s Baghdad headquarters intensified on Friday with claims that a UN official had spurned a US offer of increased protection.

The charge came as both UN and US officials acknowledged that investigators suspected that the bombers had inside assistance from Iraqi guards in carrying out Tuesday’s attack which killed at least 23 people and wounded more than 100.

“The Americans knew that there was a threat against the UN — a serious threat. They proposed to reinforce the security network around the Canal Hotel,” a European diplomatic source said.

“And the proposal was turned down by a UN officer.”

UN envoy Sergio Vieira de Mello, the highest-ranking victim of the blast, was not informed of the decision to reject a beefed up US military presence at the Canal Hotel, the diplomat added.

The United Nations has so far refused to confirm claims by unidentified US officials that the world body had spurned its offers of security assistance.

While UN Secretary General Kofi Annan conceded mistakes were made all around before the attack, he pointed the finger at coalition forces for failing to provide enough security in Baghdad and the rest of Iraq.

But even UN officials acknowledge that security at the Baghdad compound had been fatally compromised.

“They clearly had support from Iraqi security guards inside who gave intelligence to the planners of the attack,” one UN official told AFP, asking not to be identified.

“It was a well prepared attack. The target was Sergio Vieira de Mello, that much is clear,” the official said.

“They knew where Vieira de Mello’s office was and they knew they would find him in his office and they packed the vehicle with the maximum amount of explosives.”

DE MELLO’S BODY: A Brazilian air force jet carrying the body of UN envoy to Iraq Sergio Vieira de Mello took off from Baghdad airport on Friday bound for Geneva.