Suu Kyi's National League for Democracy party wants to see the constitution changed because it enshrines military power and came into force in 2008 during an era of iron-fisted army rule.
The absence from parliament of Suu Kyi and 42 other elected lawmakers who won historic April 1 by-elections was expected. The party had already said it would not attend the assembly session until the issue is resolved.
Suu Kyi's party wants phrasing in the lawmakers' oath changed from "safeguard the constitution" to "respect the constitution."
Opposition lawmaker Ohn Kyaing confirmed the opposition's refusal to attend. But he said he believed the issue would be overcome quickly because there was support within President Thein Sein's administration to change the oath.
Party officials have played down the problem, saying they still expect the lawmakers to attend the assembly, possibly this week or next.
The oath is in an appendix to the constitution, and it is unclear whether it can be changed without the approval of 75 percent of parliament.
The constitution automatically allocates 25 percent of the parliamentary seats to unelected representatives of the military, and Suu Kyi's party maintains that is undemocratic.
The document also bars people from the nation's presidency if they or any of their relatives are foreign citizens; that effectively prevents Suu Kyi from ascending to the presidency because she married a British national, Michael Aris, who died in 1999, and their two children were born abroad and do not live in Myanmar.
Thein Sein has overseen a wave of political reforms since taking office a year ago, and analysts say his administration needs the opposition in parliament to gain international legitimacy.
The by-election's outcome, in which the opposition won almost all of the 45 seats up for grabs, was considered a major step toward reconciliation after decades of military rule in Myanmar.
Wooing Suu Kyi's party to rejoin politics after it boycotted the 2010 election was a key turning point in the government's campaign for Western economic sanctions imposed during military rule to be lifted.      COPY : http://www.nytimes.com/reuters/