"We are very concerned about Ike," she said. "Any bit more of rain and Gonaives will be cut off again."
But the NHC said Ike was expected to spare Haiti a direct hit.
"But they will still get pretty strong winds and rain [in Haiti] ... as well as the Dominican Republic," warned Cristina Carrasco, an NHC forecaster.
Haiti is still battling with flooding from recent Tropical Storm Hanna, which left hundreds of people dead and hundreds of thousands of people displaced.
Teresa Bo, Al Jazeera's correspondent in the Haitian city of Gonaives, which has been submerged in water, said: "This storm has already worsened what already was a critical situation ... and there could be mudslides."
Locals are "blaming the government and the United Nations because they have not eaten anything for days," she said.
Bo said further rain is making rescue operations even more difficult.
Ike threatens Cuba
With winds near 215kph, Ike was expected to move into Cuba on Sunday or Monday, the NHC said in an advisory.
"Ike is now an extremely dangerous category four hurricane on the [one to five] Saffir-Simpson scale," the NHC said.
Ike also has the potential to strike the southern Florida Keys as it heads into the Gulf of Mexico, threatening Louisiana and the rest of the US Gulf Coast which last week weathered Hurricane Gustav.
In Gonaives, UN peacekeepers and aid workers delivered high-energy biscuits and water to storm survivors, many of whom had not eaten since Monday.
"What I saw in this city today is close to hell on earth," Hedi Annabi, a UN envoy, said.
Everton Fox, Al Jazeera's meteorologist said: "Ike is making its way away from The Turks and Caicos islands pretty quickly.
"It is moving at about 25km per hour and will steadily head towards Cuba in a direct hit."
Fox said the storm will hit Cuba "strongly" but is then expected to "low down significantly and become a category one hurricane by the time it leaves the country.
Due to a huge amount of rainfall in Cuba "there will be landslides, flash flooding and widespread devastation," he predicted.
'Hell on earth'
Dozens of children raised their hands and ran after UN food trucks that rumbled through the damp streets of Gonaives. "Hungry! Hungry!" they yelled.
Food also was brought to hungry inmates at the local jail.
The water in many neighborhoods has receded from about three metres high to about knee deep, but at least 40,000 people remain in emergency shelters.
However, the death toll in Gonaives has been reduced after Ernst Dorfeuille, the police commissioner for the city, told The Associated Press that a news report the previous evening that quoted him as saying 495 bodies had been found in Gonaives following Tropical Storm Hanna was completely wrong.
He said there were 32 confirmed deaths in this city on Haiti's west coast from the storm that hit on Monday.