A U.S. official says the United States and Cuba will resume talks on restarting direct mail service despite a deadlock between Washington and Havana over detainees that has largely stalled most rapprochement efforts.

The official said U.S. and Cuban representatives would meet in Washington for technical talks on Tuesday and Wednesday aimed at ending a 50-year suspension in direct mail. The official spoke on condition of anonymity because he was not authorized to speak to the matter publicly before Congress is notified.

The mail talks and separate negotiations on immigration have been on hold since 2009 over demands by Washington that Cuba release jailed American subcontractor Alan Gross. Washington insists Gross be released before ties can be improved. Cuba, meanwhile, demands that Washington release four jailed Cuban intelligence agents.