"We would not sentence a pregnant woman to the death penalty," he said.
Mr Nuanthasing said the trial would be conducted fairly but was unable to confirm a date.
Miss Orobator has been held at Phonthong prison, where she reportedly became pregnant in December.
The Foreign Office said the vice-consul from Bangkok, in Thailand, had been allowed into Phonthong prison to speak to her on Tuesday. It was the seventh visit from UK officials.
A spokesman was unable to comment on Miss Orobator's condition but said: "We are paying very close attention to her welfare."
Claire Algar, from Reprieve, said she was "encouraged" by the assertion that an expectant mother would not be shot but added: "She will only remain pregnant for the next however-many months."
She also said doctors and the UK Foreign Office had said Miss Orobator had become pregnant while in jail. The Laotian government has claimed she had been pregnant when arrested.
Jane Orobator has appealed for her daughter's release
Reprieve says its human rights lawyer was refused access to Miss Orobator, without explanation. The charity is urging the authorities to ensure a fair trial.
Ms Algar said: "It's very necessary that Samantha meet with a laywer and, we would say, both with a British lawyer and Laotian lawyer."
She said she was "extremely concerned" about Miss Orobator's welfare.
"People who have left [the prison] in the past have spoken about malnutrition, that they haven't received water regularly, there are no beds on which one can lie and they have also spoken of abuse," she added.
The Foreign Office has reiterated the government's opposition to the death penalty "in all circumstances" and said it took "every opportunity to make representations to the Lao authorities about our opposition to the death penalty".
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