The United States and Cuba are trying to eliminate obstacles to normal ties as the highest-level US delegation to the communist island in three decades holds a second day of talks with Cuban officials.

US objectives during today's session include the lifting of restrictions on American diplomats in Cuba and assurances that Cubans will have unfettered access to a future US Embassy in Havana.

The Americans say the resumption in full diplomatic relations depends on how quickly its requests are met.

Cuba is demanding its removal from a US list of state sponsors of terrorism, which Washington says it is considering.

Yesterday, the US said it sent additional ships to the Florida Straits to halt Cuban rafters, but rebuffed demands for broader changes to its migration rules that grant virtually automatic legal residency to any Cuban who touches US soil.

Cuba's government blames the Cold War policy for luring tens of thousands of Cubans a year to make perilous journeys by land and sea to try to reach the United States.

Still, many Cubans are worried the elimination of the rules would take away their chance to have a better life in the US.

In Washington, US homeland security secretary Jeh Johnson said America's "wet foot, dry foot" approach, which generally shields Cubans from deportation if they reach US territory, remains in effect.

But he stressed that those trying to come illegally would most likely be returned.

US officials reported a spike in the number of rafters attempting to reach Florida after the December 17 announcement that the countries would move to normalise ties. Those numbers appear to have slowed in recent days.

"Cuba wants a normal relationship with the US, in the broadest sense but also in the area of migration," said Cuba's head of North American affairs, Josefina Vidal.

She called for the US to end "exceptional treatment that no other citizens in the world receive, causing an irregular situation in the flow of migrants".

American officials instead pressed Cuba to take back tens of thousands of its nationals whom US authorities want to deport because they have been convicted of crimes. No progress was made on that issue.

The talks today are expected to focus on the broader question of how the US and Cuba can end a half-century of enmity - as promised by presidents Barack Obama and Raul Castro last month.

The nations hope to re-establish embassies and post ambassadors to each other's capitals in the coming months.