Nigeria's government has started vetting potential candidates to lead its more than 100 diplomatic missions, with appointments expected "very soon", 18 months after President Bola Tinubu recalled all ambassadors, sources familiar with the matter said.

Nigeria, Africa's most populous country and a key Western ally in the fight against Islamist insurgents in West Africa, has operated without ambassadors since September 2023.

The minister of foreign affairs has previously blamed a lack of funds for the delay in naming new diplomats.

A government source told Reuters that the issue "is being resolved" and "that means the appointment will be announced very soon."

Nigeria's security services were conducting background checks on possible appointees and had started sharing their findings with the relevant agencies within the presidency and legislature, an intelligence official told Reuters.

A spokesperson from the presidency referred questions to the foreign affairs ministry, which declined to comment. The sources declined to be named as they are not authorised to speak on the matter.

Since coming to power in May 2023, Tinubu has prioritised fixing Nigeria's struggling economy, with foreign policy taking a back seat, said a former ambassador who served in Africa and the United States.

The government has this year budgeted 302.4 billion naira ($198.30 million) to run its foreign missions.

The former Nigerian ambassador said he was informed by government officials that the issue of the absence of ambassadors in their countries had come up in discussions between Tinubu and some foreign leaders.

"Assurance had been given that they will soon be appointed," said the former ambassador, who declined to be named.