But his concerns were not passed on to senior staff and the attack went ahead on 7 May, killing three Chinese journalists and wounding more than 20 others.

The bombing - described as a "tragic error" by Nato - sparked angry demonstrations in China, where most people accused Nato, and the US in particular, of deliberately targeting the embassy.

On Thursday Pentagon officials confirmed the reports, originally made in the Washington Post newspaper.

Officer had doubts

The Washington Post's diplomatic correspondent Steve Merson: "A Pentagon analyst put an X in the wrong spot"

They said the intelligence analyst noticed surveillance photographs of the building proposed for a Nato strike did not appear to coincide with the intended target, the Yugoslav Federal Directorate of Supply and Procurement (FDSP).

The analyst did not know the building in question was in fact the Chinese embassy.

Despite repeated US apologies, the bombing has severely damaged Chinese-American relations.

At least 20 embassy staff were wounded in the attack

US Under-Secretary of State Thomas Pickering visited China last week to explain the exact circumstances of the bombing but China dismissed his explanation as unconvincing.

String of errors

It now appears the bombing was caused by a litany of mistakes.

First, CIA staff were using outdated maps and databases which did not show the embassy had moved to a new location.

Then an analyst made a mistaken assumption about the FDSP's location based on its address.

The Washington Post's diplomat correspondent, Steve Merson, told BBC Radio 5 Live he literally "put the X in the wrong spot".

Even then the situation was not lost. A second analyst noticed discrepancies between the FDSP's supposed location and that of the target building.

The US said an out-of-date map was partly responsible for the incident

Mr Bacon said: "On 4 May, this mid-level officer called a mid-level officer in Europe and conveyed his concerns, and at the same time he attempted to arrange a meeting within the CIA to clarify his concerns."

Failed to get hold of CIA

But he failed to arrange the meeting at the CIA.

He then went off for scheduled training and when he returned on 7 May he found the raid was planned for that night.

The Washington Post says there is confusion about who he rang to raise his concerns but at one point he was apparently told: "The bombers are in the air. It's too late".

US officials say the analyst was not involved in selecting the target, but took an interest because he had some knowledge of the FDSP.

Mr Bacon said the Pentagon was reviewing what happened as part of a broader review of targeting decisions.