The longtime president of Republic of Congo is going ahead with a referendum on modifying the country's constitution, a move critics say will allow him to prolong his rule.

By the time his term ends next year, President Denis Sassou N'Guesso already will have served more than 30 years in power but not continuously.

He first became president in 1979 and led the country until 1992, when he lost a re-election bid.

Five years later he returned to power and has been at the helm ever since.

The current constitution states that candidates must be 70 years old or younger, and Sassou N'Guesso is already past 70.

He said Tuesday he wants to put the issue before voters though no date has been set.