Will Donald Trump's new sanctions against Iran work?

After nearly six months of war, the US appears to be taking a different approach to Iran. President Donald Trump said Washington will carry out what he described as a 'crushing economic operation'. Attempts to reach an agreement to end the war have stalled. Now, the US is calling on other countries to join what it calls the greatest co-ordinated economic isolation in the history of the world. For its part, Iran says that any countries joining the US campaign would be treated as enemies. What does this mean for the conflict?