Despite a wave of optimism, United States and Cuban negotiators meeting in Washington on Thursday could not reach an accord on re-establishing long-fractured diplomatic ties but agreed to keep talking on Friday.

Representatives from both nations met all day at the State Department to resolve a checklist of issues before they could elevate their current diplomatic outposts known as “interests sections” into full-fledged embassies and exchange ambassadors for the first time in more than half a century.

American and Cuban officials would not discuss the talks, but a State Department notice suggested officials would speak to the news media after Friday’s round.

In recent days, diplomats on both sides had said they believed an agreement was near, while noting they still had certain issues to resolve.