BBC News with Sue Montgomery

President Obama has led the United States in a moment's silence to honour the victims of Saturday's shooting in Arizona. A single bell tolled for the six people who were killed and for the Democratic congresswoman Gabrielle Giffords, who was critically wounded. From Washington, Paul Adams.

The president and his wife Michelle stood heads bowed on the South Lawn of the White House. There were no words, and after a minute they returned inside. A little over a mile away, on the east steps of the Capitol building, hundreds of congressional staffers stood out in the freezing air in their own mark of respect. Speaking later before talks with the visiting French President Nicolas Sarkozy, Mr Obama spoke of the courage displayed by some at the scene of the shooting.