For Now, No US Embassy Opening in Havana, Officials Say

— -- While no embassy opening was announced after a fourth round of talks between the United States and Cuba, a top U.S. diplomat today called the talks "very productive" and doesn't foresee the need for a fifth round.

Instead, Assistant Secretary of State for the Western Hemisphere, Roberta Jacobson, said the details could be ironed out by the respective diplomatic missions.

Both U.S. and Cuban sources told ABC News they are optimistic an agreement will be reached on the fine details and an announcement made from respective capitals soon.

The talks come five months after President Obama and Cuban leader Raul Castro announced their intention to improve relations.

Prior to these talks, the major sticking point for Americans was the freedom for staff to move throughout the country; for the Cubans, it was courses provided to Cuban journalists by the U.S. government at the interests section in Havana, which they say fall outside normal diplomatic activities.

But both countries refused to get into the details of what remains to be worked out this time. Saying only they continue to work forward on how an embassy will function in each country.

"Fact is we are making progress on these areas," Jacobson said at a news conference. "But I'm not going to be specific on where we have to close."

"Still talking about the various aspects of the functioning of an embassy," she added. "It isn't a lack of measurement progress. Each time we have met we've made progress and made progress this time. ... Made great progress and I remain optimistic."

Cuban diplomat Josefina Vidal agreed, but also would not give details on where negotiations stood, saying the talks were respectful and productive.