By Hnin Yadana Zaw and Antoni Slodkowski
NAYPYITAW (Reuters) - Myanmar's President Thein Sein made a rare appearance at the ruling party headquarters on Monday as his newly installed leadership team prepared for a showdown in parliament with his rival, ousted party chairman Shwe Mann.
Members of the Union Solidarity and Development Party (USDP), made up mostly of former military officers, made an appeal for unity at the meeting, with the country's first free elections in 25 years due in three months.
The party, which took power in 2011 to end almost half a century of military rule, is expected to fare poorly against Nobel laureate Aung San Suu Kyi's opposition National League for Democracy in the vote.
"Today, as you see, President Thein Sein also came to meet the party members," the new chairman of the party, Htay Oo, said in a speech.
"The USDP needs to stay strong. The USDP has to be a powerful political party. Not only do we need to build a strong and united force to achieve our goals, but we also need to work together with allied political forces to win the 2015 election."
Myanmar has undergone major changes since the 2011 shift to a quasi-civilian system, but is now seeing tensions between rival forces vying for power.
The rivalry between Thein Sein and Shwe Mann - two of the major establishment figures - 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, hosted late-night meetings at the USDP complex and purged Shwe Mann's faction from the party's executive committee.
Shwe Mann still holds the powerful position of the speaker of parliament. The next act in the drama will play out on Tuesday, when Shwe Mann will face the emboldened presidential faction of his own party as the chamber reopens for the last session before the Nov. 8 vote.
The president said in his remarks it was only the second time in recent years that he had attended a USDP leadership meeting, USDP lawmaker Hla Swe said in a post on his Facebook (NASDAQ:FB) page on Monday.
The party expected Shwe Mann would respond to the events of recent days in parliament, Hla Swe told Reuters on Sunday.
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.
(This story corrects name of ruling party lawmaker in paragraphs 10,11)