Latifah Isfieh Nasser said several of the soldier's in-laws put up a futile struggle to stop the abduction by men believed to be Mahdi Army militia fighters.
U.S. military regulations forbid soldiers from marrying citizens of a country where American forces are engaged in combat. There was no immediate comment from the military about the account of the soldier's abduction.
The U.S. military has said the soldier, a linguist of Iraqi descent, was visiting family in the central Baghdad's Karadah district when he was abducted. His kidnappers used his cell phone to contact his family, it said.
The military did not identify the soldier or give further details. A massive search for him by U.S. and Iraqi forces has been under way since the Oct. 23 abduction. The in-laws said the soldier's name is Ahmed Qais al-Taayie.
The mother-in-law told The Associated Press in the family's Karadah home that her daughter, 26-year-old physics student Israa Abdul-Satar, met the soldier a year ago. The couple married in August and spent their honeymoon in Egypt.
She showed an AP reporter photographs of the couple in Cairo, one of them dated Aug. 14.
A photograph of the couple showing the soldier in a gray suit and Abdul-Satar in a red dress was on the wall of the living room in the two-room apartment, where the newlywed couple stayed when the soldier came to visit. The apartment was in a neglected, three-story building on a quiet street.
Nasser, 48, said she has 10 children, several of whom witnessed the abduction. The wife of the U.S. soldier and two of her siblings — a sister and a brother — were later taken by American troops to the heavily fortified Green Zone where they were being kept for their safety. The zone is a large area in central Baghdad that houses the U.S. Embassy, offices of the Iraqi government and parliament, as well as hundreds of American troops.
"She is so upset that she keeps threatening to take her own life when we speak on the telephone every day," Nasser said of al-Taayie's wife, who is in her final year at Baghdad's al-Mustansariyah University.
She said they did not know exactly what al-Taayie did for a living at the beginning, but that he later told his in-laws that he was a translator with the U.S. military in Iraq.
"We asked him many times not to come to visit us often. The day he was kidnapped, my husband told him not to visit too frequently because he was worried about him."
She said al-Taayie was at the apartment once every two or three months when he and her daughter were engaged. He always came at night, she recalled.
According to Nasser, the abduction of al-Taayie was preceded by an incident on the same day when a neighbor she identified as Abu Rami put a gun to the soldier's head as he was making his way on a motorbike to the nearby home of Nasser's brother, where his wife was visiting.
Abu Rami later said he was suspicious of al-Taayie because he had not seen him before in the neighborhood.
"Ahmed was frightened and his wife was crying," said Nasser. "Fifteen minutes later, a car came and stopped outside my brother's house and four armed men jumped out. They wore black pants, black shirts and white masks. They dragged Ahmed out and slapped handcuffs on him before they bundled him into the back seat of the car.
"My daughters struggled with the kidnappers. One of them broke her hand and another had her hand cut in the struggle. They were begging the gunmen not to take him," said Nasser.
One of her sons, 26-year-old Omar Abdul-Satar, and Abu Rami, the neighbor, followed the kidnappers in another car, but turned back before they could learn where the gunmen were headed. They feared that they too may be kidnapped. Abu Rami has since left the neighborhood with his family and went into hiding, said Nasser.