The event will also mark the 50th anniversary of the bloc, which was founded to jointly voice the concerns of developing countries within the UN system, Xinhua reported.
"The United Nations has confirmed to me that the UN secretary general is going to be present at the G77+China summit.
"He has decided to wholly support the national government in its organization (of the event). We are strengthened," Morales told a press conference at the presidential headquarters in La Paz.
"The success of this event will lend prestige to all Latin America," said Morales.
As this year's president of the bloc, which gathers 133 developing and emerging countries in Latin America, Africa and Asia, Bolivia has arranged to host the group's summit and anniversary celebration June 14-15.