KABUL—The U.S. government and some international Christian organizations are pressing Afghanistan to release two men who converted to Christianity, were arrested on apostasy charges, and could face the death penalty if convicted.

The U.S. has called on Afghan authorities to respect the Universal Declaration of Human Rights, a document endorsed by Afghanistan that upholds freedom of religion. "We continue to call for their release, and frequently raise this issue with the highest levels of the government of Afghanistan, expressing our strong concern," said Caitlin Hayden, spokeswoman of the U.S. Embassy in Kabul.

Afghan officials have been unapologetic. "The sentence for a convert is death and there is no exception," said Jamal Khan, chief of staff at the Ministry of Justice. "They must be sentenced to death to serve as a lesson for others." Apostasy is a capital crime in Afghanistan, where the constitution is based on Shariah, or Islamic law.

The effort to free the two men faces an uphill battle in Kabul. President Hamid Karzai is already bristling against foreign influence, after inaugurating parliament Wednesday under pressure from the West.

One of the detained men, Said Musa, 46 years old, converted nine years ago. He has worked for the International Committee of the Red Cross as a physical therapist in Kabul for over 15 years. After Mr. Musa's arrest in May, his wife and six children fled the country, fearing for their safety.