(Adds new details from captain's testimony and opening statements)
By Colleen Jenkins
FORT BRAGG, N.C., March 7 (Reuters) - Opening statements in the military trial of a U.S. Army general accused of twice forcibly sodomizing a female captain during their illicit sexual relationship provided sharply conflicting accounts on Friday of what drove the adulterous affair.
Brigadier General Jeffrey Sinclair stands accused of forcing the junior officer under his command to perform oral sex, of grabbing her genitalia against her will and of having intercourse with her in public places.
The 51-year-old general, who is married, denies sexually assaulting the captain and says the relationship was consensual, although inappropriate by military standards.
The rare court-martial of a high-ranking U.S. military official is unfolding in Fort Bragg, North Carolina, amid a growing debate among U.S. lawmakers over how best to curb sexual assault in the military.
A military prosecutor told jurors that Sinclair abused his rank and power to threaten the captain 17 years his junior to stay in a sexual relationship that spanned three years and two war zones.
"It involves a lot of consensual sex," said the lead prosecutor, Lieutenant Colonel Robert Stelle. "But it also involves lies, threats, manipulation and coercion and abuse of position to keep the relationship going."
"This is a case where non-consensual sex was used as an instrument of control," he added.
Defense attorney Ellen Brotman read excerpts aloud in court from the female captain's journal that the lawyer said help prove the liaison was based on mutual affection and remained consensual from beginning to end.
"You will see that this case is nothing more than a workplace affair," Brotman told jurors. The identity of the captain, a military intelligence officer, is being withheld by Reuters due to the nature of the charges.
"What is she saying in her journal is her biggest fear?" Brotman said. "That he still loves his wife. That's what she's afraid of."
The captain took the stand on Friday as the prosecution's first witness and recalled her initial physical encounter with Sinclair during their deployment in Iraq in 2009. She said they were watching television in his private quarters when he asked her to take down her hair and began to caress her face.
"I had developed a very strong attraction for him," she said. "On the one hand, I'm thinking how amazing it feels, but on the other hand, this is my brigade commander."
The captain, now stationed in Arizona, did not meet Sinclair's gaze during her testimony, during which the general sometimes shook his head and looked annoyed.
The junior officer also recounted how, after sex, Sinclair once threatened to kill her if she told his wife or anyone else about their relationship.
"Then he told me he would also kill my family and that he would do it in a way that no one would know it was him," she said, becoming emotional on the stand.
She said she stayed involved with Sinclair because she felt emotionally connected but also worried about how breaking things off would affect her military career.
"Weighing my options, I felt like the best way to go forward was to continue sleeping with him," she said.
The general faces life in prison if he is found guilty by a panel of five two-star generals of the most serious charge, forcible sodomy.
On Thursday, Sinclair, a one-star general, pleaded guilty to lesser offenses that carry a maximum penalty of 15 years in prison and possible dismissal from the Army.
He admitted to having an extramarital affair with the captain as well as asking other junior female officers for nude photos and viewing pornography while he was deployed in Afghanistan.
The charges saw him stripped of command in southern Afghanistan in May 2012 and sent back to Fort Bragg, where he remains on active duty. His wife is not attending the trial. (Reporting by Colleen Jenkins; Editing by Lisa Shumaker and Gunna Dickson)