Washington, Aug 30 (DPA) As the people of New Orleans gathered to mark one year after the deadly Hurricane Katrina, US President George Bush and his political critics focused on the government's failed response.

Memorial services included a moment of silence to mark the time that the hurricane unleashed fury on the Gulf Coast, the ringing of a ceremonial bell to mark the moment the first levee broke and the laying of wreaths at the locations of breaches in each of the levees that were meant to protect the city from flooding, according to broadcast images.

Those levees failed, nearly 80 percent of New Orleans stood underwater after the storm, and the half-empty city is still struggling to get back on its feet.

A human rights group on Tuesday charged that government neglect of the residents in their hour of need amounted to a human rights violation.

In a speech at a New Orleans high school, Bush accepted the mantle of responsibility for the lagging government help and vowed that his administration would keep its promises to help the Gulf Coast rebuild.

"Unfortunately, the hurricane also brought terrible scenes that we never thought we would see in America," Bush said. "I take full responsibility for the federal government's response."

All levels of government failed when responding to the storm and its aftermath, but have learned from their mistakes, Bush added.

As if to accentuate the point, Bush sent his Secretary of Homeland Security Michael Chertoff to Florida on Tuesday to oversee preparations for a much weaker storm than Katrina - Tropical Storm Ernesto, expected to hit the state by late Tuesday and Wednesday.

One year after the hurricane, images of residents stranded on the roofs of their homes as flood waters approached and of throngs of people in a shelter without food or water remain seared in public memory.

The president's critics, including Democratic members of Congress, say that the rebuilding progress has been painfully slow.

The American Civil Liberties Union said Tuesday that the government's inability to respond quickly and the suffering of the region's poor, black residents have further damaged the country's human rights record.

"As horrific as the devastation of Hurricane Katrina was, it was the government's indifference to the suffering of the poor and people of colour that truly shocked our nation and the world," ACLU executive director Anthony Romero, said in a statement.