The Vatican had a significant role in negotiations to release US prisoner Alan Gross from Cuba, according to a US Senator.
Dick Durbin, who represents the state of Illinois, has campaigned for Mr Gross' release and said he was "overjoyed" by the news.
But there were already quick objections to the news from some U.S. lawmakers.
Robert Menendez, the current head of Senate Foreign Relations Committee, denounced President Barack Obama's actions on Cuba, saying they "vindicated the brutal behavior of the Cuban government."
U.S. Senator Marco Rubio said on Wednesday he would "make every effort" to block moves by President Barack Obama toward normalising relations with the Cuban government.
"The president's decision to reward the Castro regime and begin the path toward the normalization of relations with Cuba is inexplicable," Rubio said in a statement.
The Florida Republican senator, who is Cuban-American, said he would use his role as chairman of the Senate Foreign Relations Committee's Western Hemisphere subcommittee in the new Congress to try to block the plan.
The United States and Cuba are moving to "normalise" diplomatic relations after more than 50 years of separation, President Obama is expected to announce.
Senior U.S officials, previewing Obama's forthcoming announcement, said the United States and Cuba will move to open embassies in each other's capitals, Reuters reports.
President Obama spoke on Tuesday to Cuban President Raul Castro to discuss the changes in a call that lasted nearly an hour.
As part of the relaxation in relations, Secretary of State John Kerry is expected to review Cuba's status as a state sponsor of terrorism.
"These steps will be the most significant changes to our Cuba policy in more than 50 years," a senior administration official told reporters.
"What we are doing is beginning the normalisation of relations between the United States and Cuba."
The lawyer for three Cubans held in the US on spying charges says their release today marks the end of an "arduous experience"., NBC News reports.
Gerardo Hernandez, Antonio Guerrero and Ramon Labanino were three members of a group dubbed the 'Cuban Five'.
They were accused of infiltrating groups of Cuban exiles in Florida who opposed the Castro regime.
"After 16 years of imprisonment, two years of solitary confinement and so much time spent in dangerous prisons, this is not a slap on the wrist," lawyer Richard Klugh said.
The US prisoner who has been released from jail in Cuba after five years only found out he was returning home yesterday, NBC News reports.
Alan Gross was met by his wife Judy in the Cuban capital Havana.
He was also accompanied on the flight home by three members of the US Congress - Senators Patrick Leahy and Jeff Flake and Congressman Chris van Hollen, who serves in Mr Gross' home state of Maryland.
The plane carrying Mr Gross back to America had bowls of popcorn and corned beef sandwiches - both foods he had missed during his incarceration.
Cuba has released American aid worker Alan Gross after five years in prison "on humanitarian grounds" at the request of the US, an official in Washington has said.
CNN reported a prisoner exchange that also included Cuba releasing a US intelligence source and the US releasing three Cuban intelligence agents.
Both President Barack Obama and Cuban President Raul Castro will make a statement at 5pm today on the agreement.
Gross, 65, a US Agency for International Development subcontractor, was arrested in December 2009.
He was later convicted to 15 years in prison for importing banned technology and trying to establish clandestine internet service for Cuban Jews.
A British man was grounded in Bermuda as his new wife continued to Cuba without him after drunkenly threatening the flight crew.Read the full story ›
Russian President Vladimir Putin has begun a six-day tour in Latin America, with a stop in Cuba, a key Soviet ally during the Cold War backs Moscow in its dispute with the West over Ukraine.
Russian companies will participate in petroleum projects around Boca de Jaruco on the island's north coast, and that co-operation will extend to offshore oil deposits, Cuban government website Cubadebate (in Spanish) said.
Cuban state media carried photos in the evening of Mr Putin's meeting with retired leader Fidel Castro. Mr Putin and Raul Castro also participated in a ceremony at Havana's Memorial to the Soviet Internationalist Soldier.
Its oldest stars died after a late burst of international fame, but the show will go on for just a little while longer as Cuba's trademark Buena Vista Social Club as the iconic band prepares to say "adios" with a final global tour.
Some 15 years after the release of their first recording and their historic show at Carnegie Hall, vocalist Eliades Ochoa conceded the Grammy-winning band was due for retirement.
Many of the musicians were brought out of retirement and obscurity during a legendary recording session in March 1997 produced in Havana by American guitarist Ry Cooder.
The 'Adios' farewell tour kicks off in France in July before taking in countries such as Spain, South Africa and the United States.
Former Cuban President Fidel Castro made a surprise appearance at the opening of a Havana cultural centre sponsored by one of his favourite Cuban artists.
State television broadcast images of the bearded, grey haired Cuban leader arriving at the cultural centre to the applause of local residents.
The reclusive 87-year-old was last seen in public in April 2013 at the inauguration of a school in Havana.
Castro lives in a villa on the outskirts of Havana where he regularly receives guests, but photos are rare and only occasionally do his writings appear in the local media.
Castro governed the Caribbean island for 48 years before falling gravely ill in 2006 and handing power to his brother Raul Castro, who officially became president in 2008.