Niger was waiting on Monday for a response from the West African regional bloc after coup leaders in Niamey ignored a deadline to reinstate the ousted president, a move the bloc has warned could lead it to authorise a military intervention.

The Economic Community of West African States (ECOWAS) has said it will issue a statement on its next steps in response to the junta's refusal to cave in to external pressure to stand down by Sunday following the July 26 power grab.

On Sunday as the deadline expired, the junta closed its airspace until further notice, citing the increased threat of military intervention.

ECOWAS defence chiefs agreed a possible military action plan, including when and where to strike, if the detained president, Mohamed Bazoum, is not released and reinstated.

Meanwhile, on Sunday, Italy said it had reduced its troop numbers in Niger to make room in its military base for Italian civilians who may need protection if security deteriorates.

Italy's Foreign Minister Antonio Tajani said in an interview published on Monday that ECOWAS should extend its deadline for the reinstatement of Bazoum.

"The only way is the diplomatic one. I hope that the ultimatum of ECOWAS, which expired last night at midnight, will be extended today," Tajani told La Stampa newspaper.

"It is right that he (Bazoum) should be freed, but we cannot do it. The United States are very cautious about this, it is unthinkable that they would start a military intervention in Niger," Tajani added.

Similarly, U.S. Secretary of State Antony Blinken on Friday called for "the immediate restoration of Niger's democratically elected government", and said the U.S. would pause certain foreign assistance programs that benefit the government of Niger.