Actor and activist Sean Penn on Wednesday urged more aid for Haiti as it struggles with the "enormous task" of recovering from the devastating 2010 quake.

"It would take a poet laureate to describe for you the courage and the dignity of (Haiti's) people," Penn said after accepting an award at the World Summit of Nobel Peace Laureates for his humanitarian work in Haiti.

"There are no people on earth more willing to pull themselves up by their bootstraps," Penn said.

"But as Dr. Martin Luther King said, it's fine to tell a man to pull himself up by his own bootstraps, but evil to tell a man to do so without boots."

The situation for many Haitians remains horrific more than two years after the devastating January 12, 2010 earthquake that flattened large parts of Port-au-Prince and damaged much of the south of the country, Penn said.

"Take a look at Cite Soleil some time, where 240,000 Haitians -- men, women and children -- following every light rain, sleep in a black water solution of sewage and toxins, garbage and pigs," Penn said, his voice cracking with emotion.

"Where rape and gun violence are a daily occurrence."

The magnitude 7.0 quake killed 250,000 people and displaced hundreds of thousands. According to UN figures, the quake killed, injured or displaced one in six of the Caribbean nation's entire population of almost 10 million.

Penn, who has been named Ambassador at Large for Haiti, expressed confidence in Haitian President Michel Martelly, who is trying to ramp up stalled reconstruction efforts.

"We have four years to solidify the seeding of institutions that can create sustainable democratic solutions. Four years that without a reinvigorated surge of support will leave the people's will up for grabs," Penn said.

"It's quite a task, but a doable one with investments in agriculture education, health care, housing, clean water and recognizing it's a country of nine million people, but it's also only nine million people."

Designated prime minister Laurent Lamothe told AFP last month that his country was seeking another $12 billion in aid.

But the head of the UN mission to Haiti has said that the political situation there remains "fragile" and that delays in forming a new government are hindering the recovery and economic development.

"Every time that Haiti is without a government, a prime minister and cabinet... violence and the feeling of lack of security grow," Mariano Fernandez, head of the MINUSTAH peacekeeping force, said in March.

Even before the earthquake Haiti was the poorest country in the Americas.

Penn insisted that failure is not an option and that the United States has a vested interest in Haiti's success.

"There is the human cost of poverty," Penn said.

"But if that on its own is not compelling, note that increased instability that attrition may bring to a Caribbean island (nation) an hour and half off our shores would be an open invitation to a new explosion of narco-trafficking, terrorist influences and paramilitaries."