The Rev. Jesse Jackson on Monday ended his visit to Havana without having been able to see Alan Gross, the U.S. government subcontractor serving a 15-year sentence here after being convicted of subversion.

Jackson told the foreign press that last Saturday he asked Cuban authorities to allow him to see Gross, but they told him they would need more notice to coordinate such a visit.

Nevertheless, the U.S. civil rights activist said that he spoke about the Gross case with Cuban officials.

In remarks made on Monday, Jackson expressed his hope that Gross's release can be secured and he declared that there are "open channels" between Havana and Washington to deal with this matter and that of the four Cuban espionage agents imprisoned in the United States.

Gross, 64, traveled to Cuba on behalf of a Maryland company that won a contract from the U.S. Agency for International Development to expand Internet access and the flow of information on the Communist-ruled island.

He was arrested in Cuba in December 2009 with satellite communications equipment in his possession. Havana said he was illegally aiding dissidents and inciting subversion.

In August 2012, Cuba's highest court upheld the 15-year jail sentence imposed on the American.

Cuba has hinted that it would release Gross in exchange for the return of the four members of the "Cuban Five" who remain jailed in the United States.

Washington dismisses talk of a possible swap and insists that Cuba free Gross immediately and without conditions. EFE