President Bush stood shoulder-to-shoulder with rescuers in the rubble of the collapsed World Trade Centre last night as he repeated his vow to bring the terrorists to justice.

Holding on to a firefighter for support, Mr Bush stood on top of debris to tell the hundreds of rescuers America was grateful for their work.

And as the squadron of jets patrolling the skies roared overhead, he shook hands with scores of the police, firefighters and volunteers struggling to find survivors four days after the two hijacked jets were crashed into the towers.

Using a loudspeaker fire chiefs had been using to direct operations at the site, Mr Bush said: "As we mourn our loss I would like you all to know that America today is on bended knee in prayer for the people who lost their lives here, to the workers who worked here, for the families who mourn.

"The nation stands with the good people of New York, New Jersey and Connecticut as we mourn the loss of thousands of our citizens."

One of the workers interrupted and said: "We can't hear you."

President Bush replied to cheers and chants: "Well I can hear you. The whole world can hear you. And the people who knocked down these buildings will hear all of us soon."

He continued: "The nation shares its love. Thank you for your hard work. Thank you for making the nation proud and may God bless America."

He was cheered by the workers with shouts of "USA" and "Don't let them get away".

Construction lorries around the site had been brought to a standstill as the presidential motorcade snaked its way into the heart of the devastation wrought by the terrorists.

Standing beside Mayor Rudolph Giuliani and New York governor George Pataki, Mr Bush also greeted former First Lady Hillary Clinton, now senator for New York, with a hug.

Mrs Clinton had travelled from Washington after sitting with her husband at the memorial service in the city for the dead and missing, which was attended by America's political elite, including all the living ex-presidents, except Ronald Reagan, who was too ill.

Mr Bush had arrived in New York at almost the exact time that the heavy rain, which had disrupted rescue efforts and made the area now known as "ground zero" even more treacherous, turned to sunshine.

Initially looking gaunt and drawn, Mr Bush came away from the tour visibly energised by his meeting with some of the thousands working in the effort to find survivors.

And although it is now two days since anyone has been pulled alive from the rubble, Mayor Giuliani expressed confidence that there was life amid the devastation.

"There is a real sense that there is life," said Mr Giuliani.

Police and firefighters at the scene said they were using seismic monitoring equipment in an attempt to find life and were also using sniffer dogs, but yesterday the search bore no fruit.