France's Emmanuel Macron has said he will not recognise Corsican as an official language on his first visit to the French Mediterranean island.
The president also rejected another demand by Corsican nationalists for a special residency status to prevent property speculation by outsiders.
But Macron promised more investment and said he was open to transferring more powers to local authorities.
Nationalists seeking greater autonomy won local elections in December.
Thousands of Corsicans rallied ahead of Macron's visit to call for greater autonomy from France, reports BBC.
Macron told nationalist politicians that the island was an integral part of the French Republic, but offered the symbolic move of recognising the island in the French constitution.
He did not comment on calls for an amnesty of prisoners involved in Corsica's violent campaign for independence.
Corsican regional government leader Gilles Simeoni said Macron had ‘missed an opportunity’ to develop a new relationship with the island.
Corsica already has autonomy in areas such as health and education, but it is one of France's poorest regions and many residents say they want to remain part of the republic.