The United States will pause on Sunday to remember the September 11 attacks four years ago in ceremonies overshadowed by the death and destruction wrought by Hurricane Katrina.

In a now-familiar ritual, the names of the 2749 people who died when the twin towers of the World Trade Centre collapsed under the impact of two hijacked airliners will be read out at the main memorial event at Ground Zero.

This year, the thoughts of many Americans will be focused on other victims: the estimated one million left homeless and the thousands feared killed by the hurricane which devastated the US Gulf coast nearly two weeks ago.

Both tragedies served to highlight the vulnerability of the world superpower, but where September 11 forged a sense of national unity out of trauma and anger, Katrina highlighted divisions of race and class and triggered accusations of government indifference.

In a minor departure from previous anniversaries, Sunday's memorial at Ground Zero would also reflect on those who have been killed in militant attacks outside the United States over the past four years.

US Secretary of State Condoleezza Rice will attend the ceremony, together with New York Governor George Pataki and New York Mayor Michael Bloomberg.

The Ground Zero ceremony has been tainted by controversy over the plans for a memorial museum at the site.   

Demonstration

More than 500 relatives of the September 11 victims rallied there on Saturday, protesting against proposals for an International Freedom Center that will show exhibits on freedom struggles around the world.

The demonstrating victims' families, who held up photos of their loved ones and banners that read "Preserve Sacred Ground," say the center will shift the focus away from those who died in the twin towers.

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