BAMAKO, Mali — The war against armed Islamic extremists in Mali will lose some 2,000 Chadian soldiers, the president of Chad said, leaving Malian cities more vulnerable to a resurgence of jihadist attacks.

The news that Chad will pull its troops from Mali could force France to push back its own timeframe for withdrawing its troops from its former West African colony and creates greater urgency for a U.N. military mission to Mali.

Since the French-led mission began in mid-January, soldiers from Chad have been involved in some of the fiercest fighting and are credited with some of the biggest successes to date.