President Idriss Deby had described the mission as a failure and the force was due to leave in mid-March.
But after meeting the UN’s peacekeeping chief, he said the 4,000 soldiers could stay for two more months.
Rights groups had warned that civilian aid workers needed military protection to enable them to do their work.
Chad is home to 260,000 refugees from Sudan’s war-torn Darfur region.
Discussions about the future of the UN peacekeeping mission in Chad come at a time of warming relations with Sudan.
Tensions between the two countries have been at the heart of instability in the region.
Earlier this year, the neighbours agreed to joint military patrols in the area either side of the border, and to remove the rebel troops they have influence over from near the frontier.
The extension has been agreed on the understanding that the UN’s military presence will be reduced.
But correspondents say there are hopes that the two-month window will allow further talks on the mission’s future.
Source: BBC