Recently Iran has clinched a deal with six world powers to curb nuclea

Recently Iran has clinched a deal with six world powers to curb nuclear activities. Which one among the following is not a party to it ?

USA
France
Russia
Japan
This question was previously asked in
UPSC CAPF – 2014
Iran’s nuclear negotiations were primarily conducted with the P5+1 group, which consists of the five permanent members of the UN Security Council plus Germany. The P5 are China, France, Russia, the United Kingdom, and the United States. Germany is the “+1”. This group was involved in the Joint Plan of Action (JPOA) in 2013 and the subsequent Joint Comprehensive Plan of Action (JCPOA) in 2015. Japan is not a member of the P5+1 group and was not a direct party to these negotiations or the resulting agreements.
– Parties to the Iran nuclear deal (JPOA/JCPOA): Iran and the P5+1 group.
– P5+1 members: China, France, Russia, UK, USA + Germany.
– Role of Japan: Not a direct party to the negotiations.
The Joint Plan of Action (JPOA), an interim agreement, was signed in November 2013. It aimed to freeze key parts of Iran’s nuclear program in exchange for partial sanctions relief while a long-term agreement was negotiated. The Joint Comprehensive Plan of Action (JCPOA), the comprehensive agreement, was reached in July 2015.