Raul Castro has indicated he may consider improving ties with the US Ten US congressmen are travelling to Cuba in what is thought to be the largest such delegation to visit since Fidel Castro took power in 1959. Members of the bipartisan group favour the easing of US sanctions on Cuba.
It has not been confirmed whether they are to meet the acting Cuban leader, Raul Castro, who has recently expressed an interest in improving ties.
President Fidel Castro, 80, temporarily ceded power to his brother after having emergency intestinal surgery in July.
The US broke official ties with Cuba following Fidel Castro's rise to power in 1959 and has had an economic embargo in place against the island since 1960.
Important timing
The US delegation will spend three days in Cuba, during which time members are due to meet several high-ranking Cuban officials.
The BBC's Americas editor Emilio San Pedro says the timing of the visit, coming as Cuba undergoes what could be described as its most significant internal political transformation in decades, is important.
However, it has yet to be seen if they will meet Raul Castro or whether the trip will be anything more than symbolic, our correspondent says.
The visit has been criticised by some opponents of the Castro regime in the US, including Cuban exiles in Miami, who say that economic interests should not be put before human rights in Cuba.
The Bush administration has also shown no signs of embracing a thaw as long as Cuba's communist system remains intact and political prisoners remain in jail, our correspondent adds.
'Very ill'
Acting leader Raul Castro has given several indications that he may be open to a warming of relations.
A fortnight ago, he used an address at a military parade held to mark his older brother's 80th birthday to attack the US - but also to renew an offer to hold talks with Washington.
Fidel Castro did not appear at the parade and has not been seen in public since 26 July.
His last appearance on Cuban TV, looking frail and wearing pyjamas rather than his trademark military fatigues, was in late October.
The top US intelligence official, John Negroponte, has told the Washington Post newspaper that the president is believed to be very ill and close to death.
"Everything we see indicates that it will not be much longer... months, not years," he told the Post.
Cubans polled
Meanwhile, a poll of people living in Cuba's two largest cities released by Gallup on Thursday suggests only one in four are satisfied with their freedom to choose what they do with their lives.
The poll, of 600 Cubans in Havana and 400 from Santiago, also revealed division over the performance of Cuba's leaders, with just under half approving and 40% disapproving.
On Wednesday, the top US diplomat for Latin America, Tom Shannon, criticised a greater crackdown on dissent since Raul Castro took power.
The US had also "not been able to detect there the emergence of any political figure that could be reformist", he said, and there were no clear signals about the path any future leadership would take.
Cuba's ruling Communist party newspaper Granma responded to Mr Shannon's remarks with a front-page editorial vowing to defy US efforts to bring about economic and political change on the island.
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US congressmen in rare Cuba trip
