A US soldier aims his weapon at an Iraqi being searched by another soldier near the site of the blast on Sunday. (AFP)

Baghdad, Jan. 18 (Reuters): A suicide bomber detonated half a tonne of explosives outside the US seat of power in Iraq today, killing at least 20 people in the deadliest attack since the capture of Saddam Hussein.

The explosion in the heart of the Iraqi capital came a day before a key meeting in New York between the UN, Iraq’s governing council and US and British officials on the political future of the country.

The bomb exploded at what the Americans call the Assassin’s Gate, the main entrance to the “Green Zone”, formerly Saddam’s Republican Palace complex and now the top-security civilian and military headquarters of the US-led administration.

The US confirmed at least 20 deaths, but the toll looked likely to rise. More than seven hours after the blast, soldiers were pulling bodies from the wreckage as bulldozers shovelled debris and moved shattered cars.

Officials said many of the bodies were too badly burnt or wounded to identify immediately.

Iraq’s US governor Paul Bremer has repeatedly said Washington will hand over sovereignty to Iraqis on June 30. But many Iraqis, including the most influential Shia cleric, disagree strongly with a US plan to let regional caucuses select a government rather than have direct elections.

Bremer and members of Iraq’s governing council will meet UN Secretary General Kofi Annan tomorrow to try and enlist his support for the US plan. Continuing violence 10 months after the coalition invasion of Iraq poses a serious concern for President George W. Bush, who faces an election in November.

A US military spokesman said at least two American contractors were believed to have been killed in the blast, which also wounded more than 100 people, almost all Iraqis.

The explosion shook central Baghdad and sent plumes of black smoke into the mist of the winter morning along the Tigris river. Cars blazed in the street and victims lay in pools of blood. A stream of ambulances ferried away the wounded.

US Colonel Ralph Baker said a pickup truck packed with 454 kg of explosives blew up outside the gate, where vehicles and people were lined up waiting to enter.

A Reuters Television cameraman saw a woman lying in the road, one foot blown off and a high heeled shoe still on the other. Others lay slumped on the kerb or in the roadway.

Hospitals around the capital said they had treated at least 110 people for injuries. US military officials said three US soldiers and three US civilians were among the injured.

Sunday is a working day in Iraq and the bomb went off just after 0500 GMT, when many people would have been on their way to work. Most of the victims were employees waiting to be searched before entering the complex, one witness said.

“I was passing by when the explosion happened,” Wissam Muhammad Shaker said. “People were thrown aside, three here, five there. The dead people were workers.”

Danish troops in south Iraq said today they had shot dead an Iraqi civilian who drove on when they tried to stop his car.

In Tikrit, US soldiers said two Iraqis were killed when a bomb they were planning to use against Americans exploded prematurely.