The United States and Iran are once again on a collision course over the Iranian nuclear program.
In a letter dated early March, US President Donald Trump urged Iranian Supreme Leader Ayatollah Ali Khamenei to negotiate a new deal. The new deal would replace the defunct nuclear agreement negotiated in 2015 between the United States, Iran and five other global powers.
Trump withdrew from that agreement, called the Joint Comprehensive Plan of Action (JCPOA), during his first term.