Yangon, Myanmar (CNN) -- The Myanmar opposition leader Aung San Suu Kyi and other members of her party are delaying their parliamentary debut Monday as they seek to resolve a problem concerning the wording of the oath that lawmakers have to take.
Suu Kyi and 42 other candidates from her party, the National League for Democracy, won seats in by-elections on April 1, a result welcomed by countries like the United States and Britain as a sign of progress toward democracy in Myanmar after decades of repressive military rule.
Following the elections, Suu Kyi and other newly elected opposition members were invited to attend the session of parliament this week in the capital of Naypidaw.
But they have requested that the wording of the swearing-in oath that lawmakers have to take be changed. The NLD asked the authorities to adjust the wording of the oath to say that parliamentarians will "abide by" the constitution rather than "protect" it.
"We want to change that constitution because it's not a democratic constitution," Ohn Kyaing, a spokesman for the NLD, said Sunday.
The constitution currently assigns 25% of parliamentary seats to unelected members of the military establishment.
Tin Oo, a senior NLD official, said that he believed the parliament would consider the issue Monday and that it could be decided upon this week.
The tension over the oath is the first sign of contention between the opposition and the reformist government of President Thein Sein since the by-elections.
Tin Oo said that Thein Sein, who was visiting Japan over the weekend, had agreed before the elections to amend the oath.
The snag over the oath comes as E.U. foreign ministers are expected later Monday to take action to relax many of the sanctions the European Union currently imposes on the country.
Myanmar, also known as Burma, is the top issue on the agenda of the foreign minsters' meeting in Luxembourg.
Describing the changes taking place in Myanmar as "dramatic and hopeful," Catherine Ashton, the E.U.'s high representative for foreign affairs, said in a speech last week that the bloc would "encourage European companies to look for opportunities" there.
Myanmar's authoritarian military rulers have begun loosening their grip on power after decades in which dissent was stifled and freedoms severely limited.
In the past 12 months, the government has pardoned hundreds of political prisoners, secured a cease-fire with Karen rebels and agreed to negotiate with other ethnic rebel groups.
U.S. Secretary of State Hillary Clinton described this month's by-elections as "an important step in Burma's democratic transformation."
Western governments have applauded the elections and the other recent reforms by the government of President Thein Sein. The U.S. and Australian governments eased some sanctions on Myanmar last week.
While control of parliament will not change despite the opposition's strong performance in the by-elections, the result nonetheless gives the National League for Democracy a notable presence.
Myanmar's legislature has 664 seats, more than 80% of which are still held by lawmakers aligned with the military-backed ruling party, the Union Solidarity and Development Party.
Suu Kyi led her party to a landslide victory the previous time Myanmar held multiparty elections, in 1990. But the junta ignored the results and kept her under house arrest.
Released in November 2010, Suu Kyi was allowed to crisscross the country to rally support for her party in the elections.
Last week, it was announced that she would make her first overseas trip since her detention.
Suu Kyi will travel to Norway in June to deliver the speech she was unable to give when she was awarded the Nobel Peace Prize in 1991.