Havana, Cuba (CNN) -- The lawyer representing jailed American Alan Gross has asked Cuba's president to release him for two weeks so Gross can visit his ailing mother.
"We are reaching out to you directly, with the knowledge that you have the power to grant such humanitarian requests, as you have done in the past, and with the hope that you will extend a humanitarian gesture not only towards Alan, but to his ailing mother," attorney Peter Kahn wrote in a letter to Cuban President Raul Castro.
In a statement Thursday, Kahn said that 89-year-old Evelyn Gross has a final wish: "to be able to see her son once more before her battle with cancer is lost."
Alan Gross was arrested in 2009 Cuba while working as a subcontractor on a U.S. Agency for International Development project aimed at spreading democracy.
Gross' family and attorneys argued that he had traveled to Cuba to help link the country's small Jewish community to the internet. Cuban authorities said Gross's work was tantamount to espionage.
He was convicted in 2011 and sentenced to 15 years in prison.
Kahn's statement mentions the case of Rene Gonzalez, a Cuban released from United States prison last year after serving 13 years for spying on Cuban exile groups and U.S. military installations.
Gonzalez was released on probation, while four other Cubans convicted of spying remain in jail. Cuban officials laud the men as heroes and have suggested they might agree to swap Gross for them.
Rene Gonzalez is unable to leave the United States as part of the terms of his release, but recently asked a U.S. court to be able to return to Cuba to visit his brother who is ill with cancer.
"I fully appreciate Rene Gonzalez's need to visit a dying family member," Kahn said in the statement. "We need to remember that these are real people and real lives that are profoundly affected by these decisions."
The Cuban government has not responded publicly to Kahn's request.
Officials in Washington have repeatedly said that Gross is being unjustly imprisoned.
"We have tried everything we can to free Alan Gross, who is innocent, to let him get back to be with his family," Mike Hammer, acting assistant secretary of state, told reporters in Washington last week. "It is an unjust imprisonment and we hope that this issue is resolved as soon as possible. ... It is an issue that we work very hard on every day here."