Nov. 27, 2013  -- The sister of the young American man who has been held in Iran for two years on espionage charges said his family is "absolutely" more hopeful that the former Marine will be returned safely to them following Iran's agreement on an interim nuclear deal.

Sarah Hekmati, sister to jailed Amir Hekmati and family spokesperson, told ABC News Tuesday that the family "can only imagine" the landmark international deal, signed over the weekend, "is good news" for her brother.

"If they can agree to these negotiations, it opens the door for them [the U.S. government] to keep raising Amir's case, and for [Iran and the U.S.] to keep communicating with each other," Sarah Hekmati said. "I can't see it as something bad."

State Department spokesperson Jen Psaki told reporters Tuesday that while the delicate Geneva negotiations focused "exclusively on nuclear issues," the State Department has "repeatedly raised" the case of detained American citizens "in our bilateral discussions with Iran, including President Obama's phone call with [Iranian] President [Hassan] Rouhani in September." Another State Department spokesperson declined to comment to ABC News, however, on whether those discussions have resulted in any concrete progress with Hekmati's case or any others.

Now 30 years old, Amir Hekmati, an Iranian-American born in Arizona, was arrested in Tehran in August 2011 while his family said he was visiting his grandmothers. Sarah Hekmati said the family did not know what had happened to Amir until he suddenly appeared on Iranian state television in December 2011 where he "confessed" to being a spy sent into Iran by the CIA. Later Amir was convicted and sentenced to death, but that sentence was overturned.

READ: American Held in Iran as CIA 'Spy' Had No Military Intel Training

In an exclusive interview shortly after Amir's initial broadcast, Amir's father, Ali Hekmati, called the Iranian allegations "a bunch of lies." A U.S. official said at the time Amir was "obviously under duress and in the hands of the enemy" when he made his confession. In September this year Hekmati reportedly penned a handwritten letter to Secretary of State John Kerry in which he said his confession was "obtained by force, threats, miserable prison conditions and prolonged periods of solitary confinement," and said he had "committed no crime."

But in recent months historically icy relations between the U.S. and the Middle Eastern nation appear to have warmed considerably as the U.S. has dealt with the newly-elected President Rouhani, rather than his notoriously hostile predecessor Mahmoud Ahmadinejad. Obama's call with Rouhani in September was the first direct contact between the heads of state since 1979.

The White House Tuesday released a carefully-worded statement that "respectfully" requested Iran help return another American, former FBI agent Robert Levinson, who disappeared in Iran in 2007. Tuesday marked the day Levinson became the longest-held American, at 2,455 days – nearly seven years.

Unlike Hekmati, Levinson was not arrested, but simply vanished from Kish Island off Iran's southern coast. The Iranian government has denied holding him, but American officials and analysts suspect Iranian officials are linked to his unidentified captors, who have sent the Levinson family "proof of life" videos and pictures.

READ: Obama Asks Iran for 'Safe Return' of Former FBI Agent

Another Iranian-American, pastor Saeed Abedini from Idaho, was arrested in Iran and sentenced to eight years for what the State Department said were his "religious beliefs." The U.S. government has also repeatedly called for Abedini's release.

The release of the Americans would be a "critical good will gesture" by Iran, according to Rey Takyeh, a Council on Foreign Relations senior fellow and former State Department senior advisor on Iran.

"I don't know if it [would mean] they have had a change of heart of the U.S., but it's an important and critical test of Rouhani's authority. It's a critical test of the Islamic Republic's understanding that it needs to improve the atmosphere of the talks and not just the substance of the discussions," Takyeh said of further nuclear negotiations. "I suspect, at least on the two Americans that are imprisoned [Hekmati and Abedini], you may see some movement. I'm not sure if all of these three cases will be resolved at the same time… but you might see some movement."

For more information on Amir Hekmati's case, CLICK HERE to visit a website set up by his family.

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