Secretary of State John Kerry issued a statement "respectfully request[ing]" that the Iranian government release a former U.S. Marine whom it has detained since 2011 on the suspicion that he is a spy.

"[T]his Memorial Day also marks another milestone: 1,000 days since an American veteran, Amir Hekmati, was unjustly detained while he was visiting his family in Iran," Kerry said Monday.

"Mr. Hekmati has spent almost three years in an Iranian prison on false espionage charges. We remain especially concerned about reports of Mr. Hekmati’s health in prison. Mr. Hekmati’s family in the United States has endured the hardship of his absence for too long. He is the eldest son, and his family misses him and needs him home. We respectfully request that the Government of the Islamic Republic of Iran release Mr. Hekmati so that he may be reunited with his family in the United States."

Kerry's request comes on the same day that the Daily Caller reports Iran's supreme leader, Ayatollah Ali Khameini, has denounced the United States as an "oppressor" of Iran.

“Battle and jihad are endless because evil and its front continue to exist," Khameini is quoted as saying. "This battle will only end when the society can get rid of the oppressors' front with America at the head of it, which has expanded its claws on human mind, body and thought."

Hekmati isn't the only American jailed in Iran. Pastor Saeed Abedini has been sentenced to eight years in prison for his Christian faith, while his wife and children live in Idaho and hope for his release. "In addition, ex-FBI Agent Robert Levinson is believed to be held there, although the Iranian government denies it," according to Fox News.

Abedini spent the last two months in a hospital, but he was brought back to jail last week. "The Iranian guards did not just take Pastor Saeed into custody," Jay Sekulow of the American Center for Law and Justice wrote. "No, they beat him severely. So severely that he passed out. We know these details because all of this was witnessed by Pastor Saeed's parents, who were visiting him when the guards stormed the hospital. They were shocked and helpless. They could do nothing as the guards took their son back to Rajai Shahr Prison."