Suu Kyi complains of irregularities in Myanmar election YANGON (Reuters) - Attempts to disrupt campaigning for Myanmar's historic by-elections on Sunday are "beyond acceptable," opposition leader Aung San Suu Kyi said on Friday, her first public appearance since falling sick last weekend. What has been happening in this country is really beyond what is acceptable for a democratic election. Still, we are determined to go forward because we think that is what our people want," a frail but defiant Suu Kyi told reporters outside her lakeside house in Yangon. She accused her rivals of vandalizing election posters, padding electoral registers and "many, many cases of intimidation," including two attempts to injure candidates with catapulted projectiles. The United States and European Union have hinted economic sanctions - imposed years ago in response to human rights abuses - could be lifted if the election is free and fair, which could unleash a wave of investment in the impoverished but resource-rich country bordering India and China. To be regarded as credible, the vote needs the blessing of 66-year-old Suu Kyi. She is contesting one seat in her first election since being freed from house arrest in late 2010. Suu Kyi's National League for Democracy (NLD), competing for 44 of the 45 by-election seats, has previously complained of irregularities that could undermine the vote. As big as France and Britain combined, Myanmar's size, energy resources and ports on the Indian Ocean and Andaman Sea have made it a vital energy security asset for Beijing's landlocked western provinces, and a priority for Washington as President Barack Obama strengthens engagement with Asia. "There have been cases of vandalism of NLD signboards and posters and many, many cases of intimidation," said Suu Kyi, who fell ill on March 25 due to seasickness and exhaustion while campaigning by boat. She said she remained "a little delicate." Much is at stake in Sunday's vote. Some U.S. restrictions such as visa bans and asset freezes could be lifted quickly if the election is credible, diplomats say, while the EU may end its ban on investment in timber and the mining of gemstones and metals. There are bound to be complaints on election day. After 49 years of isolation and often brutal army rule, Myanmar has limited experience in holding ballots. The 2010 election was widely seen as rigged to favor the military-backed Union Solidarity and Development Party (USDP), the biggest in parliament. Most diplomats say they believe Myanmar's rulers are sincere, and that Suu Kyi and her NLD party would increase parliament's legitimacy, but the NLD appears to be leaving itself room to contest the results. As well as alleging irregularities, it claims that the president, who is supposed to be impartial, has tried to influence the vote. The government has invited in a small number of election observers, including five from the Association of Southeast Asian Nations, but they have been given hardly any time to prepare inside Myanmar. Additional reporting by Andrew R.C. Marshall; Editing by Jason Szep and Daniel Magnowski