The loan will help meet the 837-million-franc ($862-million) cost of a complete renovation of the 1930s-era Palais des Nations, the European headquarters of the UN.
In a statement, the federal government said: “The maintenance of the Palais des Nations in Geneva is of the utmost importance for Switzerland as a host state.
“Ensuring that the UN has a modern real estate portfolio is a fundamental prerequisite for strengthening Geneva's position as a city where the global challenges of our time are tackled.
“In view of asbestos materials found in the building and potential fire hazards, a complete renovation is urgently needed to ensure the safety of those who use it and to equip it for the needs of the future.”
The renovation project, planned for 2017, will also aim to improve the building's energy efficiency and disabled access.
Built between 1929 and 1936, the Palais des Nations originally housed the League of Nations, before its successor the United Nations was formed in 1945.
Now the second largest UN centre after New York, the Geneva building hosts around 10,000 meetings a year.
It's also a major tourist attraction for Switzerland, with over 100,000 visitors a year taking a tour in one of 15 languages.
The renovation project must be approved by the UN General Assembly by the end of this year if it is to begin in 2017.
The works are expected to take eight years to complete.