"I promise you I will return to Malacañang because I am only on leave," he told supporters of the Laban ng Demokratikong Pilipino-Puwersa ng Masa coalition during a campaign rally at the Plaza Pershing in this city Tuesday night.
It was the first time Estrada publicly announced his plan to take back the presidency since he was forced out of office by a military-backed uprising on Jan. 20.
Estrada insisted he is the rightful leader of the land, having been voted to office by more than 10 million Filipinos in May 1998.
He warned the "elite" and his detractors who conspired to oust him that "they will suffer the consequences the moment I am back in power."
"The elite and the wealthy businessmen, they are the ones who keep on borrowing from government funds. But they don’t pay it back so there is nothing left for the poor," he told the crowd in Filipino.
His words were met with chants of "Erap pa rin! Gloria resign!" by more than 5,000 supporters.
Earlier, the Supreme Court (SC) said it would come out with a ruling on Estrada’s petition by March 13. The former leader had questioned the legitimacy of President Arroyo’s presidency and insisted he was merely on leave.
Estrada pointed out that he never signed a resignation letter and was forced only to abandon Malacañang Palace to avoid bloodshed as protesters massed outside its gates in the morning of Jan. 20.
Re-electionist Sen. Miriam Defensor-Santiago, who is running under the opposition coalition, assured the people that the SC will rule in favor of Estrada since the issue is "strictly constitutional."
"The issue of legal status involves interpretation of constitutional provisions, and not political by any means," she said.
In her rally speech, Santiago stressed that democracy is the rule of the majority. "It is undemocratic to claim that an EDSA crowd could possibly reverse the rule of the majority of voters."
In Manila, Justice Secretary Hernando Perez said yesterday the government was ready to accept any court verdict, but warned that any decision favoring Estrada could upset the public.
State prosecutors were set to file graft charges against Estrada last week, but the SC prevented them from doing so for 30 days while it studies the petition.
Perez acknowledged "there is a possibility" that the SC could rule in favor of Estrada, but said he was optimistic the former president’s ouster was justified.
He said an early ruling by the SC would be good for the country, citing the decision of some foreign businessmen to suspend investment plans until the court issues a decision.
He said the legal efforts of Estrada to reclaim the presidency were frightening off investors.
"Potential investors, especially foreign investors, are asking questions about the status of the government," Perez said. "The entire country and the entire world is watching us."
He added that the legal challenge has also intimidated potential witnesses against the former president.
"Some witnesses who want to testify against Estrada on corruption cases also do not want to come out in the open until the court makes a decision," fearing Estrada could punish them if he is reinstated, Perez said.
Estrada is under investigation for alleged economic plunder, misuse of funds, violations of the anti-graft law, perjury, bribery and possession of unexplained wealth.
Prosecutors in the impeachment trial claimed the deposed president amassed as much as P15 billion in bribes and kickbacks during his 31 months in office.