Myanmar opposition leader Aung San Suu Kyi pays a visit to her constituency in Kawhmu outside Yangon on Tuesday. NEW: Suu Kyi will deliver Nobel lecture when she visits Oslo in June Suu Kyi's party has requested that the wording of lawmakers' oath be altered Myanmar's president is to visit Japan this week Suu Kyi's party won 43 of the 44 seats it contested in by-elections April 1. She is scheduled to attend her first session of parliament Monday after she was elected in the constituency of Kawhmu. Nyan Win said the National League for Democracy was waiting for Myanmar authorities to respond to the request. News of the complication emerged as Norway announced that Suu Kyi would visit the country in June, her first overseas trip in 24 years. She was released from years of house arrest in 2010. While in Oslo, Suu Kyi will deliver the Nobel lecture she was unable to give when she was awarded the Nobel Peace Prize in 1991, Nobel spokeswoman Merci Olsson said. Suu Kyi was under house arrest in 1991 and so could not travel to Norway. Her son, Alexander Aris, delivered an acceptance speech on her behalf. British Prime Minister David Cameron invited Suu Kyi to visit the United Kingdom in June when he met her last week in Myanmar. Suu Kyi responded, "Two years ago, I would have said, 'Thank you for the invitation but sorry,' but now I am able to say, 'Well, perhaps' -- and that's great progress." Cameron reflected that Suu Kyi was allowed to leave Myanmar for some of the past two decades but had not done so because she knew the regime would not let her return. 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." The U.S. and Australian governments eased some sanctions on Myanmar this week. Clinton visited Myanmar in December, a historic trip marking the first time a secretary of state had been to the country in more than 50 years. And in another sign of improving ties between Myanmar's government and other countries, Thein Sein will visit Japan this week, the Japanese Ministry of Foreign Affairs said Wednesday. Thein Sein will meet with Prime Minister Yoshihiko Noda. 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. Released in November 2010, Suu Kyi was allowed to crisscross the country to rally support for her party in the elections. CNN's Per Nyberg and Yoko Wakatsuki contributed to this report.