Cuban President Raul Castro has urged the US to end its trade embargo after the two countries opened formal talks on restoring diplomatic relations.
He said the five-decade embargo "caused enormous human and economic damage".
But only the US Congress has the power to lift the embargo, and correspondents say many Republicans are still deeply opposed to this.
On Wednesday, US President Barack Obama and Mr Castro agreed a number of measures to improve ties.
They included the release by Cuba of US contractor Alan Gross and three Cubans held in the US.
Read more: Relations between the US and Cuba have been frozen since the early 1960s when the US broke off diplomatic relations and imposed a trade embargo after Cuba's revolution led to communism.