One American prisoner has lost six teeth from malnutrition. Another tried to kill himself. A third, a Briton, is traumatized by the possibility her sentence could be doubled.

They are among the foreign nationals incarcerated in Iran on spying or sedition charges, a continuing source of tension in that country’s relations with Western nations, particularly the United States and Britain. Many are Iranians with dual citizenship.

Now, the prisoner issue is heating up as President Trump threatens to derail the nuclear agreement with Iran and possibly revive onerous American sanctions.

Nearly two years after a group of American captives in Iran was freed when the nuclear accord took effect — in return for the release of a group of Iranians held in the United States — there is speculation that another prisoner exchange may be sought.