Protest is mounting in the case of a pregnant Christian woman who faces a death sentence in Sudan for not renouncing her faith, as her husband recently found her shackled to the wall of her cell.

U.S. Senators Kelly Ayotte (R-N.H.) and Roy Blunt (R-Mo.) wrote a May 16 letter to Secretary of State John Kerry asking that he give "full attention to the outrageous Sudanese court ruling that sentenced Meriam Yaha Ibrahim Ishag to death by hanging for her religious beliefs."

They urged "full diplomatic engagement" to secure the release of her and her son and to offer her political asylum.

Daniel Wani, a Christian and U.S. citizen, was not able to visit his wife Meriam until this week, according to Tina Ramirez, executive director of the U.S.-based religious freedom group Hardwired.

"Once he was able to, she was shackled and her legs were swollen," Ramirez told Fox News.

Ibrahim, 26, is eight months pregnant. She is imprisoned with her 18-month-old son in a Sudanese jail after a May 15 court ruling convicted her of apostasy from Islam and adultery.

She is recognized as Muslim under Sudanese law because her father was Muslim. However, she was raised as a Christian by her Ethiopian Orthodox mother after her father abandoned the family. She was convicted of adultery because the law does not recognize marriages between Muslim women and Christian men.

Ibrahim rejected the charges and refused to renounce her faith, telling the court, "I am a Christian and I never committed apostasy."

According to reports, members of her father's family reported her to authorities, claiming she had changed her name. They submitted documents they said proved she had been Muslim from birth.

Ibrahim's attorneys, who are appealing the sentence, said the documents are forgeries.

Wani cannot have custody of his son because the boy is considered a Muslim and is not allowed to be in the custody of a Christian man.

The married couple has several businesses, including a farm, south of Khartoum. Wani has returned to Sudan from New Hampshire, where his brother Gabriel Wani also lives.

"I'm just praying for God. He can do a miracle," Gabriel Wani told the New Hampshire news station WMUR. "Everyone is depressed. You don't believe it. It's shock."

Ibrahim's death sentence will not be carried out until she gives birth and finishes nursing her baby.

Her conviction has caused international outcry.

A U.S. State Department spokesperson on May 15 said the State Department is "deeply disturbed" by the death sentence. It urged the Sudanese government to "respect the right to religious freedom."

"We call on the Sudanese legal authorities to approach this case with the compassion that is in keeping with the values of the Sudanese people," the spokesperson said.

Numerous lawmakers and human rights advocates have called for greater action by the U.S. government and international bodies.

U.S. Rep. Trent Franks (R-Ariz.), a co-chair of the U.S. Congress' International Religious Freedom Caucus, called on the State Department to express to the Sudanese government that such a human rights violation "will be taken extremely seriously" and that Sudan must follow its obligations under international treaties.

"Such blatant disregard for the value of human life – and religious freedom – is an indescribable disgrace," he said May 15.

Senators Ayotte and Blunt asked Kerry and President Obama to reappoint an Ambassador at Large for International Religious Freedom, saying this position's primary purpose is to "monitor, prevent, and respond to this exact type of incident." The ambassador position has been vacant since October 2013, when the previous ambassador stepped down.

A petition from the American Center for Law and Justice's Be Heard Project calling for Ibrahim's release has gathered over 200,000 signatures.

The U.S. Commission on International Religious Freedom, a body that advises the U.S. government, strongly condemned the death sentence and called for Ibrahim's immediate release.

"This case and the sentencing are a travesty for religious freedom and human rights in Sudan," commission chairman Robert P. George said May 16.

"International attention to this case is critical to holding the Sudanese government accountable for its constitutional provisions and international commitments to protect and respect freedom of religion or belief not only for Mrs. Ibrahim, but all Sudanese, regardless of faith," he stressed.

Since 1999, the U.S. State Department has agreed with the commission's recommended designation of Sudan as a "country of particular concern" on religious freedom issues.

U.S. Rep. Frank Wolf (R-Va.), a co-chair of the Tom Lantos Human Rights Commission, condemned the "draconian" sentence against the woman. He asked President Obama to appeal for Ibrahim's release and offer her "safe haven."

"The clock is ticking," he stressed.