Talks between the United States and Cuba failed to nail down an agreement on restoring diplomatic ties and will stretch into a new round, officials from both sides said Friday.
"Both delegations agreed to continue our exchanges on issues related to the functioning of diplomatic missions, so we will continue those conversations in the next few weeks," the head of the Cuban delegation, Josefina Vidal, told reporters after two days of talks.
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She refused to go into detail about where the differences lay between the Cold War foes, who are seeking to overcome half a century of enmity and restore normal ties.
The fourth meeting between the two sides ran into an unscheduled second day on Friday at the State Department in Washington.
"This has not been an easy task given our complicated history," top US diplomat for Latin America Roberta Jacobson told reporters in a separate press conference.
"This round of talks was highly productive," she added, saying that "we have made significant progress in the past five months" and the two sides were "much closer" to reopening their respective embassies.
In a ground-breaking move, President Barack Obama and Cuban President Raul Castro agreed in December to seek a normalization of relations frozen for five decades.
"But we're still talking about various aspects of the functioning of an embassy," Jacobson said Friday, refusing to be more specific about the sticking points.
The United States has so far announced it plans to remove Cuba from a blacklist of state sponsors of terror, which should happen around May 29 after a 45-day review period by Congress.
Havana has also found a bank willing to handle its financial affairs on US soil, something which had been a major hurdle.
But the communist authorities in Havana have been particularly angered by US democracy programs and have so far not met demands that American diplomats be allowed to meet freely with dissidents.