United Nations 

On 21 April 2003, United Nations Secretary-General Kofi Annan sent a letter to Heads of State and Prime Ministers addressing the strategic importance of WSIS and inviting them to take part in the first phase of the Summit in Geneva (Switzerland) from 10-12 December 2003.

 Switzerland 

January-April 2003, Swiss President Pascal Couchepin invited Heads of State and Government to Switzerland on the occasion of the first phase of the Summit (Geneva, 10-12 December 2003).

 International Telecommunication Union 

On 9 July 2003, International Telecommunication Union Secretary-General Yoshio Utsumi sent an invitation letter for the Geneva phase of the Summit to Ministers of Foreign Affairs, International Organizations, CEOs of ITU Sector Members and accredited business entities and to accredited NGOs and Civil Society entities.