Iran and the United States volleyed tweeted criticisms of each other into Sunday over the fate of prisoners in both countries, underlining that separate negotiations outside of Tehran’s tattered nuclear deal continue between the nations. The tweets from two Iranian Foreign Ministry officials also signaled the waning influence of outgoing President Hassan Rouhani’s administration, which in August will cede power to President-elect Ebrahim Raisi, a protege of Iran’s Supreme Leader Ayatollah Ali Khamenei. The spat began on Saturday with Abbas Araghchi, Iran’s head negotiator in nuclear talks in Vienna, writing that those discussions must “obviously await our new administration.” However, Araghchi added that America and Britain must “stop linking a humanitarian exchange—ready to be implemented—with the” nuclear deal. “Keeping such an exchange hostage to political aims achieves neither,” he wrote on Twitter. “TEN PRISONERS on all sides may be released TOMORROW if US & UK fulfill their part of deal.” …