Clinton’s planned visit to Papua New Guinea has also been scrapped.
Ms Clinton said she had been personally floored by the Haitian disaster.
“It is biblical, the tragedy that continues to stalk Haiti and the Haitian people,” she said, adding that the outlook for Haiti had been slowly stabilising before the quake.
“We had private business beginning to make investments … There was so much hope about Haiti’s future. Hope that had not been present for years. And along comes Mother Nature and just flattens them.”
The international Red Cross says it has unlocked emergency funds and is mobilising supplies for a “massive” aid operation in Haiti following the country’s devastating earthquake.
A spokesman for the International Federation of the Red Cross and Red Crescent Societies, Jean-Luc Martinage, said “a massive international aid operation was needed”.
“Emergency stocks are prepositioned in Haiti and will allow us to bring aid to 3,000 families for three to four days,” he said.
“But we’ll have to swiftly bring relief supplies from our regional disaster response centre based in Panama.
“The most urgent needs at this time are search and rescue, field hospitals, emergency health, water purification, emergency shelter, logistics and telecommunications.”
Mr Martinage said supplies in Haiti included kitchen kits, personal hygiene kits, blankets and containers for storing drinking water.
Six federation relief experts are due to fly into Haiti from Panama to support the Haitian Red Cross and help coordinate international relief.
A Red Cross team was also due to lead a crucial assessment of the damage in Haiti along with European Union experts that will allow relief agencies to gauge aid needs.
The federation said the area most affected by the 7.0 magnitude quake was Port au Prince, and the West Province with a population of 2.2 million.
The UN Office for the Coordination of Humanitarian Affairs indicated that areas immediately to the west of the capital suffered the full force of the quake.
The International Committee of the Red Cross (ICRC), which has staff in the country, said medical needs and clean water supplies would be “considerable in the short term”.
“Everything that’s infrastructure isn’t working,” said ICRC spokesman Simon Schorno.