The content originally appeared on: CNN (CNN)Iran and the United States return to Vienna on Tuesday for another round of talks aimed at reviving the 2015 nuclear agreement abandoned by the Trump administration. There have been enough indications of progress from both sides to suggest that negotiations have entered a critical phase, but a number of issues remain unresolved. Those include the scope of sanctions relief for Iran, sequencing of events, verification mechanisms, Iran's compliance process, Tehran's demand for guarantees […]
