"He would not have come to Havana if he didn't have a hope of obtaining results," a Western diplomat, speaking anonymously, said in reference to the possible release of Gross. The diplomat added that Havana "will never hand over a prisoner to American officials," but could release Gross on humanitarian grounds and allow him to go back with Carter. There are also plans for Carter to meet with Cardinal Jaime Ortega, archbishop of Havana, who had a major hand in the release over the past few months of dozens of imprisoned Cuban dissidents. And the former US leader is expected to hold a news conference before leaving Cuba on Wednesday. US diplomats expressed hope last week that the former president, who was awarded the Nobel Peace Prize in 2002, could use his influence to prod Havana into releasing Gross. The 61-year-old contractor was arrested in December 2009 for delivering laptops and communications devices to Cuba's small Jewish community. The Carter Centre, a Georgia-based non-profit organization founded by the former president, issued a statement last week announcing the trip, but it made no mention of the Gross case. US officials in Havana made clear however that Washington would welcome his help.

"We're hoping that he will talk with the Cuban government to ask for a humanitarian release and if the Cuban government could please consider it, hopefully immediately," Molly Koscina, spokeswoman for the US diplomatic mission in Havana, told AFP Friday. The Carter Centre said the ex-president also wanted to learn about Cuba's planned economic overhaul, which calls for major layoffs from the public sector and new rules allowing small-scale private enterprise.

"The trip is a follow-up to their May 2002 visit to Cuba. It is being undertaken as a private, nongovernmental mission under the auspices of the not-for-profit Carter Centre," it said. The centre also said it would "discuss ways to improve US-Cuba relations." Carter, who was US president from 1977-1981, visited Cuba in 2002 he met with then-president Fidel Castro, the country's revolutionary leader. He called at the time for an end to the US embargo on the island. He also called on the regime to allow UN human rights officials to visit Cuba, and publicly praised the Varela Project, a pro-democracy petition calling for a referendum on increased freedom of expression and amnesty for political prisoners. Carter met during that visit with leading Cuban dissidents Oswaldo Paya and Elizardo Sanchez. That year, Carter won the Nobel Peace Prize for his decades of work seeking to end conflicts and advance human rights.