YANGON - The party of Myanmar opposition leader Aung San Suu Kyi expressed grave concern on Friday for her health while she is in prison facing charges that carry a jail term of up to five years.

It is learnt that Daw Aung San Suu Kyi has not been able to sleep well at night because she gets cramps in her legs day after day, the National League for Democracy (NLD) said.

Nyan Win, one of Suu Kyi's lawyers, said the court decided to delay final arguments in the case until June 5. The final hearing was to be held on Monday.

They did not give us a reason, he told Reuters.

The 63-year-old Suu Kyi was moved from her home to a guest house in Yangon's notorious Insein Central Prison on May 14 to face charges of violating her house arrest. Only days earlier, she had been treated for low blood pressure and dehydration.

The NLD said she is in desperate need of proper medical treatment and we are very much concerned about her health.

Suu Kyi has spent more that 13 of the past 19 years in some form of detention, and activists fear for her health if she is convicted, as is widely expected.

She faces a three to five year prison term if found guilty of breaking the terms of her house arrest by allowing an American intruder to stay for two days after he swam to her home on May 4.

The case has been condemned by the West as a show trial to keep Suu Kyi detained during the regime's promised elections next year, dismissed by critics as a ploy to entrench nearly a half century of military rule.

Myanmar's Southeast Asian neighbors have warned the trial threatened the military government's honor and credibility, but rejected calls for tough action against the ruling generals.

The regime lashed out at its critics on Thursday, accusing them of meddling in its affairs and denying the prosecution of Suu Kyi was a political or human rights issue.

The American intruder, John Yettaw, has told the court that God sent him to warn Suu Kyi that she was going to be assassinated by terrorists.

Suu Kyi has denied any prior knowledge of his plans and blamed the incident on a security breach, for which no officials have been punished.

Suu Kyi is accused of breaking the terms of her house arrest under a draconian state security law. Her lawyers argue she was charged under a section of the law that is no longer valid because it is based on the 1974 constitution abolished years ago.

Suu Kyi's two female housemates and Yettaw are charged under the same security law. The American is also accused of immigration violations and breaking a municipal law that bans swimming in Inya Lake where Suu Kyi's home is located.