YANGON  - Myanmar's opposition leader Aung San Suu Kyi on Saturday called for her once-banned party to unify amid concerns that internal squabbles could undermine its push for power at historic polls in 2015.

Speaking at the first ever congress of her popular but politically callow National League for Democracy (NLD) party, Suu Kyi urged a revival of the "spirit of fraternity" which saw it build a huge base during iron-fisted junta rule.

But she acknowledged "there was some fighting" within the party, something analysts attribute to the reluctance of an elderly cabal of senior advisors -- veterans of the democracy struggle -- to give way to an eager younger generation.

"We have to act with restraint" the Nobel Laureate, who is expected to be re-elected as party chairman on Saturday, said urging delegates not to fight over positions.

"The spirit of fraternity is very important. We have been strong in the past because of this spirit."

Although hugely popular in Myanmar some experts question whether the NLD is ready to run an impoverished nation whose economy, education and health systems were left in tatters by the corrupt former junta. The party is expected to win national elections in 2015, if they are free and fair.

But experts say it must first resolve internal divisions which again flared ahead of the conference as four members were banned from attending, accused of trying to influence the voting.

Hundreds of delegates, many clad in the orange jackets of NLD party members, heard Suu Kyi address the issue of party chairmanship -- a position she currently holds -- and urge delegates to elect a "leader who is in accord with this era, in accord with this country and the party".

The congress is the latest sign of the dramatic changes seen in Myanmar since a quasi-civilian regime, led by former general Thein Sein, took power in 2011, ending years of isolation and heralding a flood of aid and investment.

The 67-year-old Suu Kyi has not ruled out ambitions of becoming president, with elections set for 2015, but a constitutional rule now bars her from the role as she was married to a Briton and has two sons who are foreign nationals.

But doubts persist over whether her opposition party can remodel itself for the challenges of government, with many senior members -- known as the "NLD uncles" -- in their 80s and 90s refusing to make way for younger members.

"They could not take power over the country tomorrow, they are not ready. They have a lack of capacity," a western diplomat observing the congress told AFP, requesting anonymity.

"I think they understand more and more that they have to catch up and study and learn and they should use the next two years to do that."

The NLD also faces the financial and political might of President Thein Sein's Union Solidarity and Development Party (USDP), created by former generals who shed their uniforms to run for office in controversial elections held in 2010.

The USDP, which was battered by the NLD in by-elections held in April last year that saw Suu Kyi elected to parliament, is also scrambling for a new strategy to avert a major defeat in 2015.