In a televised address on Saturday, Aristide said his resignation was "out of question". He said suggestions he might step down were fabricated by his foes.
"These are baseless rumours spread by leaders of the opposition to provoke the population and cause disorder in the country," Aristide said.
But as the president talked tough, capital Port-au-Prince slipped further into anarchy with reports of looting and indiscriminate killings.
Armed fighters, who have vowed to oust Aristide, took over Mirebalais, less than 60km from Port-au-Prince, and now control more than half of the Caribbean nation.
Rule of law is non-existant in
Rebel leader Guy Philippe said his forces would be in the capital within days.
In the capital, Aristide loyalists put up barricades around the presidential palace as thousands of people looted warehouses at the port.
Journalists were threatened and many motorists said they were forced to hand over money or even their cars to pro-government gangs.
A gas station was left in flames and the driver of one car said his vehicle had been stoned and he had to make an emergency reverse to escape.
Alarmed by the sweeping lawlessness, the White House directly blamed Aristide for the current crisis and questioined "his fitness to governor Haiti".
"This long-simmering crisis is largely of Mr Aristide's making," White House spokesman Scott McClellan said in a statement.
"His failure to adhre to democratic principles has contributed to the deep polarisation and violent unrest that we are witnessing in Haiti today," he said.
"His own actions have called into question his fitness to continue to govern Haiti."
Earlier, the US embassy in Haiti said the gangs had begun to burn, pillage and kill and demanded action from Aristide.
"This long-simmering crisis is largely of Mr Aristide's making"
White House spokesman
"The armed gangs that are spreading terror and attacking civilians and the general population are acting in the name of Jean-Bertrand Aristide," the embassy said in a statement.
"We therefore urgently call on President Aristide to issue the necessary instructions so that his supporters stop this blind violence against the civilian population and public and economic targets.
"Mr Aristide must understand that his honour, legacy and
reputation are now at stake."
It added that it was equally important for the rebels to halt
their advance "in order to spare the capital from violence
additional to that currently being perpetrated on Port-au-Prince by pro-government gangs".
UN chief Kofi Annan said he was "increasingly concerned at the alarming deterioration of the security and human rights situation in Haiti."
But Aristide said he had a responsibility to stay in office, despite the gains by rebels and the international pressure to stand down.
Again warning that thousands could be killed by the rebels, Aristide told CNN: "I have the responsibility as an elected president to stay where I am, protecting the people the way I am, the way I can, asking the US and international community to stand against terrorists."
With the fall of Mirabalais into rebel hands early on Friday nearly all of Haiti's major cities are now held by the insurgents with the exception of Saint-Marc, 96km from Port-au-Prince, which is under the nominal control of police loyal to Aristide.