Iran and P5+1 countries have successfully reached an agreement on nuclear development programs through the Joint Comprehensive Plan of Action (JCPOA) on 14 July 2015. The agreement gives hope that tensions between Iran and the Western countries, especially US, would end in line with the signing of the agreement. However, when the US administration was taken over by Donald Trump, the hope was dashed when Trump refused to ratify the nuclear agreement on 13 October 2017. Trump considered that the JCPOA agreement to be the worst that involved US. Trump also claimed that Iran was a fanatical regime and made multiple violations of the agreement. Trump who is regarded as a populist and conservative always adopts a policy that conflicts with the views of the public. Consequently, the populist and conservative Trump's personality is seen to have played an important role in every policy adopted. Iran's nuclear future has become uncertain as Trump refused to ratify the nuclear agreement. Dispute between the two countries is likely to occur and the relationship would be more strained, similarly when Iran was under the administration of Ahmadinejad.