Former New Mexico Gov. Bill Richardson's recent visit to Cuba was private in nature and the release of a U.S. aid contractor sentenced to 15 years in prison for subversion was not on the agenda, the Communist government in Havana said.

The governor, who vowed last week to remain on the island until authorities allowed him to visit 62-year-old Alan Gross, left Cuba on Wednesday.

"Richardson came to Cuba on his own initiative and we received him at his request, on a private visit," the Cuban Foreign Ministry said in a statement issued after the U.S. politician's departure.

"The release of Gross was never on the table during the preparations for his visit, which was made clear to him as soon as he brought it up," the statement said.

Richardson's "request to see the prisoner, which he did not signal in advance, became impossible due to his defamatory comments to the press, in which he described Alan Gross as a 'hostage' of the Cuban government," the ministry's North America desk officer, Josefina Vidal Ferreiro, said.

She said the government was also irritated by the governor's public vow not to leave Cuba without seeing Gross.

"Richardson was reminded that Cuba is a sovereign country that does not accept blackmail, pressure or arrogance," Vidal said.

"For humanitarian reasons," she said, the Cuban government "has facilitated meetings with Gross for U.S. figures who have visited the country and have requested it in a private, discreet and respectful way."

Gross' health is normal for someone of his age and medical history, according to Vidal.

"He receives conscientious medical attention, which the U.S. Interests Section (in Havana) was able to corroborate during a Sept. 9 consular visit," the foreign ministry official said.

"I have been here a week and tried through all means - with religious institutions, diplomats from other countries, all kinds of efforts - and I see that this isn't going to change," Richardson said Tuesday said at a press conference in Havana. "So why would I stay?"

"Perhaps the Cuban government has decided it does not want to improve relations. Perhaps that is the message it is sending," the former governor, lawmaker, ambassador and Cabinet secretary said.

Noting his years of advocating for better U.S.-Cuba ties, Richardson said he was "very disappointed and surprised" by Cuban officials' unwillingness to let him see Gross or even to discuss the case.

It was the second time Richardson traveled to Havana in a bid to secure the release of Gross, while former President Jimmy Carter made a similar attempt six months ago.

Gross, a sub-contractor for the U.S. Agency for International Development, was arrested Dec. 3, 2009, in possession of satellite communications equipment he said he was planning to distribute among Cuba's Jewish community.

Havana says he was illegally aiding dissidents and inciting subversion on the Communist-ruled island.

Last month, Cuba's highest court upheld the 15-year jail sentence imposed on Gross in March.

The case has increased friction between Cuba and the United States, which have not had diplomatic relations since 1961, though each country maintains an interests section in the other's capital.

Gross has lost around 45 kilos (100 pounds) while in custody and is ailing and depressed, Richardson said Tuesday, stressing the "humanitarian element" of the affair.

While here, Richardson met with Cuban Foreign Minister Bruno Rodriguez and with the island's Catholic primate, Cardinal Jaime Ortega.

The governor said that though Rodriguez raised the issue of the five Cuban spies held in U.S. prisons, there was no discussion of exchanging Gross for the intelligence officers.