Sudan is facing growing international condemnation after a woman was sentenced to death and forced to give birth while shackled to a prison floor for marrying a Christian.
The US State Department described the case of Meriam Ibrahim (27) as "horrific" and continues to press Sudanese officials to intervene.
Muslim women in Sudan are forbidden from marrying out of their faith - but although Ms. Ibrahim has a Muslim father, she claims to have been brought up a Christian as that was her mother's faith.
A court rejected this argument and found her guilty of apostasy in renouncing Islam and adultery for marrying a Christian, Daniel Wani.
Ms. Ibrahim was sentenced to 100 lashes and death by hanging earlier this month - but her killing was suspended for two years so she could nurse her daughter Maya, born on a floor on Wednesday after guards at Omdurman Women's Prison refused to release her.
"We're concerned about this horrific case, and we've expressed that many, many, many times" State Department spokeswoman Jen Psaki said.
"We'll continue to press through every channel we can our concerns about this case".
Former US Secretary of State Hillary Clinton is the latest high-profile tweeter to express outrage about the case following posts from Mia Farrow and Richard Branson.
"Meriam Yahya Ibrahim's death sentence is abhorrent" Mrs. Clinton wrote. "Sudan should stop threatening religious freedom and fundamental human rights".
Meriam Yahya Ibrahim’s death sentence is abhorrent. Sudan should stop threatening religious freedom and fundamental human rights.
— Hillary Clinton (@HillaryClinton) May 24, 2014
US embassy officials have been attending Ms. Ibrahim's public hearings and are monitoring the appeals process in Khartoum. She remains incarcerated with her newborn baby and 20-month-old son.
Mr. Wani - a US citizen - said on Thursday his wife and children were holding up well.
"As for the new situation, her psychological condition seems to be slightly better and Martin (the son) is also in good condition and is not naughty as was the case before. And the girl, of course she is still small, she's in good health".
Both the US and British governments have summoned the country's charge d'affaires to discuss the case - which Mr. Wani is hoping will be reviewed.
"I hope they will take another look at the case - they will find many flaws, enough to cancel the judgement or close the case" he said.
Islamic sharia law has been in force in Sudan since 1983.
