NAYPYITAW (Reuters) - Myanmar's ruling party leaders gathered for a hastily arranged meeting in the country's capital on Monday to prepare for a showdown with their ousted party chairman in parliament.

Rivalry between two of Myanmar's most powerful establishment figures - President Thein Sein and ruling Union Solidarity and Development Party (USDP) chairman Shwe Mann - came to a head in a late-night drama on Wednesday, when trucks with security personnel sealed off the headquarters of the party.

Thein Sein sacked Shwe Mann before the president's allies, under the presence of the security personnel, went to the USDP complex to host a late night meeting and purge Shwe Mann's faction from the party's executive committee.

The developments came just three months before the country's first free election in 25 years.

On Monday, Thein Sein attended the meeting at USDP headquarters, USDP lawmaker Hla Shwe said in a post on his Facebook page.

The president's cavalcade swept out of the monumental party complex about twenty minutes after the closed-door party meeting was scheduled to start.

Shwe Mann still holds the powerful position of the speaker of parliament. He will face the emboldened presidential faction of his own party on Tuesday when the chamber reopens for the last session before the Nov. 8 vote.

The party expected Shwe Mann would respond to the events of recent days in parliament, Hla Shwe told Reuters on Sunday.

At the meeting on Monday, party members may discuss how to introduce a bill to parliament that could be used to impeach Shwe Mann, Hla Shwe said.

Under the bill, if one percent of constituents sign a petition and the electoral commission finds their complaint justified, their member of parliament can be recalled.

Shwe Mann faces a petition from his own constituents for supporting a bill in parliament to reduce the military's political power.

Myanmar's electoral commission sent a letter to Shwe Mann on Thursday that has featured prominently in state media, requesting he table a vote on the bill.

Shwe Mann has said little since his sacking on what he plans to do, and he has not responded to the letter.

In a Facebook post on Saturday, he said he would do nothing to endanger the country or the people, and that neither should anybody else.