Niger’s military junta has severed military ties with its former colonial ruler France, firing some of the previous government’s key ambassadors.

It also warned citizens of the West African nation to watch for foreign armies and spies as a regional delegation's efforts at negotiation quickly deadlocked.

The junta's announcement on state television late Thursday deepens the post-coup isolation for what had been the United States and allies' last major security partner in the Sahel, the vast region south of the Sahara Desert that various armed groups have turned into the global center of terrorism.

With two days remaining before a deadline set by the West African regional bloc to release and reinstate President Mohamed Bazoum or face possible force, Bazoum in a plea published in a Washington Post opinion piece said, "I write this as a hostage" and urged the U.S. and partners to help.

Niger’s mutinous soldiers face a Sunday deadline set by the regional bloc known as ECOWAS, whose envoys arrived Thursday for talks. But those discussions quickly stalled, with the delegation unable to meet the coup leader, Gen. Abdourahmane Tchiani, or go into the capital, Niamey, according to a person with close knowledge of the talks who spoke on condition of anonymity because they weren't authorized to comment.

The junta’s announcement brought further skepticism about any deal. It said it was terminating the military agreements and protocols signed with France and announced the end of functions for Niger’s ambassadors to France, the U.S., Togo and neighboring Nigeria, which is leading ECOWAS efforts on dialogue.

"All aggression or attempt at aggression against the state of Niger will see an immediate response and without warning," said a spokesman for the coup leaders, Col. Maj. Amadou Abdramane, with the exception of Mali, Burkina Faso and Guinea, which have expressed support for the coup. Mali and Burkina Faso have said such an intervention would be a declaration of war against them.

Bazoum wrote that Niger’s security situation had been improving before the coup, in contrast to neighboring Mali and Burkina Faso that are led by military juntas, but said that's now at risk because Niger would lose aid from foreign partners and extremist groups would take advantage of the country’s instability.

"In our hour of need, I call on the U.S. government and the entire international community to help us restore our constitutional order," he wrote.

France has 1,500 military personnel in Niger, which had been envisioned as the base for counterterror operations in the region after anti-French sentiments grew elsewhere.

The U.S. has 1,100 military personnel in Niger, including at a key drone base, and indicates it's reluctant to leave, especially with the growing influence of the Russian private military group Wagner in the Sahel.

ECOWAS has been unsuccessful in stemming coups and is trying to change course with Niger in a region that has seen five of them in the past three years – two each in Mali and Burkina Faso.

The ECOWAS delegation is led by former Nigerian head of state Gen. Abdulsalami Abubakar. A second group led by Ambassador Babagana Kingibe has gone to engage with the leaders of neighboring Libya and Algeria, said Ajuri Ngelale, special adviser to Nigeria's president.

But analysts said they’re not putting much faith in talks.

"I don’t expect mediation efforts to bear fruit in the short term. The junta is digging in ... Seems like uncharted territory," said Alex Thurston, assistant professor of political science at the University of Cincinnati.

Niger’s roughly 25 million people live in one of the poorest countries in the world, and any cuts in foreign aid could be disastrous. Already, citizens are feeling the effects after ECOWAS suspended all commercial and financial transactions between its member states and Niger and froze Nigerien assets held in regional central banks.

The bloc’s sanctions include halting energy transactions with Niger, which gets up to 90% of its power from Nigeria, according to the International Renewable Energy Agency.

Earlier this week, power transmission from Nigeria to Niger was cut off, an official at one of Nigeria’s main electricity companies said, speaking on condition of anonymity because they were not authorized to comment.