Leading international press advocacy groups on Tuesday protested the U.S. government's refusal to grant visas to two Cuban journalists trying to return to their jobs at the United Nations after a brief vacation back home.

Paris-based Reporters Without Borders called on the U.N. secretary-general's office to intercede on behalf of Tomas Granados Jimenez and Ilsa Rodriguez Santana, a married couple who have covered the United Nations in New York for Cuba's official Prensa Latina news agency since 2005. Their U.N. accreditation is valid until early next year.

The U.N. "must demand an explanation from the U.S. State Department and ensure that Granados and Rodriguez are able to return to their posts," Reporters Without Borders said.

The Committee to Protect Journalists issued a similar statement from New York.

"We are concerned by the decision of the U.S. authorities to deny the renewal of visas to Prensa Latina reporters accredited to cover the United Nations," Carlos Lauria, the committee's senior program coordinator for the Americas, said in the statement. "We urge U.S. authorities to explain the reasons for their action."

American officials have not responded to requests for comment.

Prensa Latina has said that U.S. authorities in Havana did not explain why the couple's visas were refused. Instead, the reporters received a document referring to a regulation authorizing the U.S. president to deny entry to anyone considered a threat to the country.

"This measure is both persecutory and incomprehensible," the Reporters Without Borders statement said. "Since when could journalists who have been accredited to the United Nations for three years suddenly pose a 'threat' to the United States?"