US and Cuban negotiators on Friday opened a second round of historic talks aimed at overcoming half a century of enmity and restoring full diplomatic ties.

The negotiating teams met at the State Department just before 9:00 am (1400 GMT) for round two, after an initial meeting in Havana last month broke the ice but ended with little sign of a breakthrough.

The talks are building on US President Barack Obama and Cuban president Raul Castro's surprise announcement in December that the two Cold War adversaries had decided to normalize relations severed in 1961.

The US side in the talks is represented by Roberta Jacobson, assistant secretary of state for Western Hemisphere affairs, who faced Josefina Vidal, the Cuban foreign ministry's director for US affairs, across a long table flanked by their respective delegations.

Neither said anything during the few minutes journalists were allowed into the room to record the encounter. Press conferences were scheduled for later in the day.

A senior State Department official said the negotiators would review provisions in the Vienna Convention on Diplomatic Relations on such subjects as the freedom of movement of diplomats and the use of diplomatic pouches.

The hope is that within the coming months both nations will agree to reopen embassies in each other's capitals and appoint fully-fledged ambassadors. Currently they operate with so-called interests sections in Havana and Washington.

US President Barack Obama is due to attend the Summit of the Americas in Panama on April 10-11, which Cuba will also attend for the first time.

Observers believe both nations, long mired in tension stemming from the Cold War, are keen to relaunch full diplomatic relations around that date.

But after more than five decades of hostility and suspicion, steep obstacles remain to renewing diplomatic ties.

This is seen as the first step towards a full normalization of relations between the United States and the communist-run Caribbean island, which has been governed since a 1959 revolution by revolutionary leader Fidel Castro and now by his brother Raul.

Ahead of the talks, both sides staked out their positions.

Cuban officials demanded that, as a preliminary step, Havana be stripped of its US designation as a state sponsor of terrorism -- a label which has plagued the island since 1982, and which among other sanctions has complicated access to the global banking system.

Washington, however, has insisted that its ongoing review of the terror blacklisting should not be linked to the restoration of diplomatic ties.

In return, the US has insisted that its diplomats and embassy be granted full powers under the Vienna Convention to operate freely, including meeting with Cuban dissidents.

"I certainly think that our presidents and my secretary would be delighted if we could have everything worked out in time for the Summit of the Americas," a senior State Department official told reporters ahead of Friday's talks.

"But that depends a lot on how our counterparts come to the table prepared to get things done and whether they are comfortable with the things we need in order to run an embassy the way we do in other places around the world."

Friday's talks may be a "little bit disappointingly workman-like in their nature this time. But this is where we roll up our sleeves as diplomats and sit down at the table and make sure that we hammer out all of the details out to get embassies up and running."

Restoring diplomatic ties "doesn't take very long if we get agreement on things," the official added.

Obama has called on the US Congress to lift the decades-old biting economic embargo of Cuba.

But some lawmakers -- as well as parts of the Cuban dissident community -- remain wary of the diplomatic demarche, arguing Obama has failed to secure guarantees about progress on human rights.

One of the aims of Friday's meeting is to set a date for the first ever US-Cuba discussion on human rights.

Although no date has been set, "it will be the first time that we would be able to sit down with the government directly and have an in-depth conversation about our differing perspectives," the State Department official said.