PORT-AU-PRINCE - Haitians on Wednesday grieved for the nearly quarter of a million people wiped out in last year's earthquake, while praying for their beleaguered country to be given another chance.

Crowds were expected to attend a Catholic Mass at the ruined cathedral in the capital Port-au-Prince early Wednesday to pray for the more than 220,000 people killed almost instantly in the magnitude 7.0 quake on January 12, 2010.

The boisterous, often raucously noisy street life that typifies this Caribbean nation was to give way to somber reflection, with a minute of silence at 4:53 pm, the moment that disaster struck.

On Tuesday, officials and relatives of victims began commemorations by gathering at a mass grave on a windy hillside outside Port-au-Prince. President Rene Preval joined mourners who laid flowers and wreaths at the base of simple black crosses.

Later, religious leaders held prayers at the University of Notre Dame in Port-au-Prince. There had been "an earthquake of the heart," one priest said in his address.

"Let the heart of the people never cease to beat for charity and liberty."

The ceremony was broadcast live on public television, which carried the words on the screen, written in Creole: "12 January 2010. 4h53. We will not forget you."

The anniversary finds Haiti barely healed from the trauma inflicted 12 months ago and gripped by political instability over the holding of a runoff round in elections to replace Preval.

The economy and infrastructure are crippled, a cholera outbreak continues to kill, and more than 800,000 people live in squalid tent camps, according to a new official count. Rebuilding has hardly begun.

Former US president Bill Clinton, one of the main figures coordinating a massive international aid effort, arrived Tuesday to join ceremonies and said he was "frustrated" by the slow pace of reconstruction.

He also called on the government "to resolve" the election standoff.

However, he did say he was "encouraged" that after repeated delays in organizing the flow of aid money and the implementation of promised projects, "we are doing much better."

The UN, meanwhile, said that Haiti's recovery would be an "absolute priority" for the world body in 2011. US President Barack Obama took up the call, urging the international community to "fulfill the pledges it has made."

The huge tasks here include clearing rubble, moving people out of tents and back into houses, halting widespread environmental degradation, and rebuilding an education system that currently provides schooling to less than half of all children.

On Wednesday South Korea's Sae-A Trading said it would invest $78 million to open a textiles factory, creating up to 20,000 jobs and making it Haiti's largest private employer, but it will be years before the plant goes online.

One of the more immediate concerns is the cholera outbreak, which has so far claimed 3,759 lives, according to the latest Haitian government update, and sickened thousands more.

The World Health Organization said Tuesday that the "peak has not been reached," although the death rate was slowing.

The most overriding issue to resolve will be the stalemate in holding a second round in the presidential election to replace Preval.

International monitors from the Organization of American States (OAS) are due to issue a report with non-binding recommendations to Preval on how to move ahead with the runoff after first-round results sparked deadly riots.

According to a leaked draft of the report, the OAS is calling on Preval's favored successor Jude Celestin to drop out because of fraud.

Celestin would give up his place to the previously third placed candidate, singer Michel Martelly, who would then face Mirlande Manigat, a former first lady who won the most votes in the first round.

The switch, if confirmed, would be a blow to Preval, who is due to leave power and had been hoping to see his ally take over.

Some observers fear Haitians could face a renewal of rioting that claimed five lives after last month's announcement of preliminary results.

However, Preval has said he will only discuss the report once anniversary commemora/sstions are over.