In a meeting Sunday with relatives of a U.S. Marine imprisoned in Iran, Vice President Joe Biden said a "good atmosphere" has been created with the Islamic Republic to work toward the release of Amir Hekmati, according to his family.

Biden met Sunday in Detroit with the family of Hekmati, who was arrested in August 2011 on allegations of spying for the CIA while visiting his ailing grandmother and other relatives in Iran. During his nearly four-year imprisonment, Hekmati has been drugged, whipped and told a heartbreaking lie that his mother died in a car accident, his family said.

Sunday's meeting with the vice president renewed the family's hope that Hekmati will be freed, the man's sister, Sarah Hekmati, told FoxNews.com.

"He was very understanding and supportive and he reassured us that Amir has been a priority since the beginning," Sarah Hekmati said. "We felt good about the meeting."

"He wanted to let us know Amir is not forgotten," she added. "He said there's a good atmosphere that’s been created for them to discuss Amir's case [with Iran]."

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She said Biden asked the family's permission to make the Marine Corps veteran's plight "more public." Shortly after the private meeting with the Hekmati family, Biden's office took to Twitter:

Hekmati was taken into custody in August 2011 on accusations of espionage for the CIA. In December of that same year, Iranian state television aired a videotaped confession from the leatherneck in which he had stated that he had sneaked into Iran to establish a CIA presence. His family said at the time that he was coerced into making the statement.

In January 2012, Hekmati was sentenced to death, but the ruling was overturned two months later, after the Iranian Supreme Court ordered a retrial. Two years later, Hekmati is still awaiting a new day in court. His family told FoxNews.com last month month they believe the recent "framework" nuclear agreement between the West and Iran will help to free the Marine.

Biden's visit came days after Hekmati was reportedly taunted by prison guards who told him President Obama called for the release of another prisoner in Iran during the White House Correspondents Dinner on April 25, but did not mention his name.

According to the family, Hekmati called his mother from the notorious Evin prison in Tehran and told her what the prison guards had said to him, KMBZ.com reported.

In an emotional letter to the White House shortly thereafter, Sarah Hekmati demanded to know why President Obama has never publicly mentioned her brother's name.

"Why has President Obama yet to utter the name Amir Hekmati?" his sister wrote. "Why on days significant for Amir -- Memorial Day, Veterans' Day, the anniversary of his death sentence, the anniversary of his imprisonment -- President Obama cannot say the name Amir Hekmati out loud, but he can say it for Jason Rezaian and he can say it for Pastor Abedini? Why when we make a request is it ignored? Why am I forced to write this email to you AGAIN, the same subject AGAIN, the same plea AGAIN?"

Obama mentioned Hekmati in a written statement in March about U.S. citizens detained or missing in Iran. He also personally raised Hekmati’s case in September 2013 during a phone call with Iranian President Hassan Rouhani, but has never publicly mentioned Hekmati's name.

Secretary of State John Kerry met last week in New York with his Iranian counterpart, Iran's Foreign Minister Mohammad Javad Zarif, but a read-out of that meeting has yet to be released by the State Department.

The White House has repeatedly said that negotiations on Iran's nuclear program are separate from other matters -- cautioning that other issues, such as the release of American prisoners, could harm efforts to reach a deal on the country's nuclear ambitions.

Sarah Hekmati said that while the administration publicly says the talks are separate, they are "definitely parallel."

"It’s been a long draining process and we just want it to be over with," she said.