"It is a sad fact that the Philippines has a legacy of political corruption. While that legacy will not be erased overnight, we have made tremendous strides," Arroyo told investors, diplomats and industry leaders on Friday.
"We call on our political leaders of all parties and preferences to look to our future … to ensure stability for the sake of the nation."
A day earlier officials warned of plots to assassinate the president and bomb foreign embassies, a move critics say was intended to derail Friday's demonstrations.
The government, concerned about communist rebels planning to infiltrate the protests, brought armoured army reinforcements and set up checkpoints at key points across the city.
Captain Carlo Ferrer, a military spokesman, said intelligence reports indicated the rebels planned "to create confusion and chaos".
On Wednesday, the rebels vowed to intensify attacks to weaken the government.
|Organisers said the security alert was to stop|
people from attending the rally [AFP]
The assassination plot allegedly involved a sniper ready to attack when an opportunity arises, Hermogenes Esperon, the Philippines military chief of staff, said.
One of the protest organisers, Renato Reyes, scoffed at the allegations as a "very desperate tactic to create an atmosphere of terror" and prevent people from joining the protest.
Esperon denied the move was to scare people, saying that as security forces they have deemed it necessary to "come out in the open about our assessment of the situation".
Speaking to Al Jazeera, Ramon Casiple, executive director for the Institute for Political and Electoral Reform, said the political crisis is all about the government being the custodian of public money.
He said the Philippine economic progress has not been felt on the ground and there is a general perception that there is big-scale corruption within the government.
In a related development, a leading Chinese telecommunications company implicated in the Philippines corruption allegations warned that the scandal could affect bilateral trade.
ZTE Corp allegedly offered huge kickbacks to a former Philippine elections chief and Arroyo's husband if they could clear a national broadband contract for the company.
Both men have denied the accusation, and Arroyo scrapped the deal last year.
Howard Xue, a ZTE spokesman, said the company "cannot allow itself to be dragged into any political circus" and dismissed an appearance at the Philippine senate hearing.
"ZTE has neither done anything wrong, nor has it bribed anyone to get this project," he said, noting that China has overtaken the US as the Philippines' biggest trade partner.
"This episode certainly brings unforeseeable negative influence on bilateral economic cooperation between China and Philippines."