America commemorated the victims of the man-made catastrophe which struck it four years ago, even as it struggled to cope with the massive natural disaster on the country's Gulf Coast that has underlined how the US remains far from equipped to deal with a new version of 11 September 2001.
For a brief time, minds turned from Hurricane Katrina to the 2,983 who died that day in New York, at the Pentagon in Washington, and in rural Pennsylvania. It was a perfect early September morning, just like the one four years ago, which carried no hint of the disaster that was about to unfold.
At the empty site of the World Trade Centre, now just a giant 16-acre hole extending six storeys deep, brothers and sisters of the dead read out the roll-call of loved ones' names that has now become an anniversary ritual. In his speech, Mayor Michael Bloomberg said New Yorkers' hearts also turned to the even greater numbers suffering in the wake of Katrina, and to the victims of the 7 July bombings in London, "our sister city". In keeping with the now established tradition, the ceremony halted for silence at 8.46am, 9.03am, 9.59am and 10.29am - the first two the exact times that the hijacked planes slammed into the towers, the last two when the south tower and then the north one collapsed. At sunset, two shafts of light representing the twin towers were to be beamed into the night sky over lower Manhattan.
In Washington, George Bush, his wife, Laura, and most of the cabinet gathered on the South Lawn of the White House to observe a minute's silence at 8.46am, before the President left for his third visit in 10 days to the hurricane-ravaged areas of Louisiana and Mississippi.
In his weekend radio address, Mr Bush urged his countrymen to show the same spirit of national unity as in their response to the 2001 al-Qa'ida attacks.
"Today America is confronting another disaster than has caused destruction and loss of life," he said.
In a separate ceremony at Arlington National Cemetery, Donald Rumsfeld warned that further terrorist attacks were more than possible. "I wish I could say that ... we were gathering to commemorate a danger long since past," the Defence Secretary said, as he laid a wreath in honour of the victims. "But we cannot. The enemy continues to plot attacks, and the danger they pose to the free world is real and present."
In New Orleans, New York city firefighters helping with the aftermath of Katrina held their own brief ceremony to remember their 343 colleagues who died on 9/11. Afterwards the men - all volunteers - returned to patrolling the streets and joining in the search for the dead and the evacuation of residents willing to leave.
From the stricken city, the news is starting to grow a little less grim.
Though the toxicity of the remaining floodwaters is if anything rising, their levels are receding as breached levees are repaired and more pumps come on line. Half the city is now clear of water, and officials reckon it could be fully drained within a month.
The grisly process of collecting corpses continues. But it now appears that the final death toll - though certain to rise steeply from the present 154 in Louisiana and 211 in Mississippi - will fall well short of the 10,000 once feared dead in New Orleans alone.Reuse content