Opposition groups seeking to oust President Gloria Macapagal Arroyo (search) on vote-rigging allegations said Monday they'll consider impeachment when Congress convenes next week. Two more of her close aides announced their resignations.

Eleven Cabinet members have also quit during the seven-week crisis, and former allies have urged Arroyo to do the same, but she has remained firm, saying she committed no crime. She admits talking to an election official before being declared winner in May 2004, but denies she manipulated the election.

Her advisers on investor relations and good governance confirmed their resignations Monday.

Left-wing opposition groups and supporters of ousted President Joseph Estrada (search), who backed Arroyo's main election rival, the late Fernando Poe Jr., (search) have staged almost-daily rallies calling for her ouster, including one last week that attracted about 40,000 people.

The administration responded with a pro-Arroyo rally on Saturday, mustering up to 100,000 people in Manila. Arroyo's spokesman, Ignacio Bunye, on Monday insisted "the Cabinet is being reorganized and revitalized and we are working toward restoring political and economic stability."

Next week, the protracted battle shifts to Congress, where the minority opposition will push for an impeachment trial in the Senate.

Arroyo has said she was ready to face trial to rebuff the allegations of electoral fraud, and House minority leader, Rep. Francis Escudero (search), said the opposition was reluctantly following the impeachment path. Arroyo is to deliver her annual state of the nation address, officially opening Congress, on July 25.

The government appears confident it can prevent lawmakers from hearing evidence of wiretapped conversations between Arroyo and the unidentified election official because the recordings were illegally made. If the complaint is rejected, the constitution says no other impeachment can be filed within a year.

But what happens in Congress will depend on rules of impeachment agreed to by lawmakers, including whether the wiretap evidence is admissible.

Escudero said the opposition was carefully weighing options "because of the rules, not because of the numbers, not because of evidence."

"We have to have the rules first and study these rules," he said. "Why are they trying to rush us into impeachment? ... The president's resignation is the easy way out for the country."

One third of the House's 236 members must approve any impeachment motion before it can go to the Senate, which would act as a trial court.