Chad's President Mahamat Deby said the decision to terminate the country's military pact with France was taken because it had become outdated, in his first public remarks since the surprise announcement last week.

In a speech delivered late on Sunday, Deby said the pact no longer aligned with Chad's security or geopolitical needs. Chad has struggled with a jihadist insurgency for over a decade, and backing by French and US troops has failed to bring stability.

"This rupture is part of our will to build a Chadian army that is more autonomous, more committed, and more responsible in the defence of the homeland," Deby said.

Until recently, the West had considered Chad an important ally in the fight against jihadists in the Sahel. Groups linked to Boko Haram and Islamic State are active in the country's Lake Chad region on its southwestern border.

In October, around 40 soldiers were killed in a brazen attack on a military base, after which Deby threatened to withdraw the Central African country from a multinational security force made up of countries that border Lake Chad.

Deby's decision to end the pact with France could force all French troops to leave after being stationed there over six decades since the country became independent. Chad ordered out the small contingent of US forces based there this year.

Deby said the agreement failed to provide substantial military value to the country amid various challenges, including terrorist attacks. He said Chad remained open to work with all partners, including France.

"This agreement was signed in a different era, with distinct actors on both sides and under a completely different context. Over time, this agreement has become obsolete," he said.

France has been forced to pull its soldiers out from Mali, Burkina Faso and Niger, following military coups in those West African countries and growing anti-French sentiment.

The US is meeting a similar fate in the region. Last summer, Niger ordered the closure of its new, multimillion dollar spybase which underpinned military operations in the Sahel after talks with Washington soured.

The French drawdown, coupled with a US pullback from Africa, contrasts with the increasing influence of Russia and other countries, including Turkey and the United Arab Emirates, on the continent. Russian mercenaries are helping prop up the military governments of Niger, Mali and Burkina Faso, and are fighting alongside them against Islamist militants.

"This decision was not taken lightly," Deby said. "It is the result of in-depth reflection and careful evaluation. It fulfils a commitment made to the Chadian people."