Iran will be formally approved as a member of the SCO at the meeting of heads of state later on Tuesday.
"I am confident that Iran’s full-scale membership will contribute to the SCO cooperation in different fields by bringing new practical content and opening broad prospects," Zhang told Sputnik.
The SCO chief praised Iran’s efforts related to the accession process and expressed support for Tehran’s constructive and effective participation in the organization’s cooperation agenda.
"The SCO expansion is a natural process and not an intentional attempt," Zhang added.
The SCO is an international organization founded by China, Kazakhstan, Kyrgyzstan, Tajikistan, Russia and Uzbekistan in 2001.
In 2017, India and Pakistan were admitted as members.