Eritrea's neighbours say they are still considering its request to rejoin the East African body, Igad, after initially saying they welcomed its bid to end years of isolation.
Igad's Executive Secretary, Mahboub Maalim, told the BBC that the process of rejoining the regional body was in the "very early, preliminary stages".
Eritrea is under UN sanctions for its alleged support of Somalia's al-Shabab.
Analysts say rejoining Igad could be aimed at avoiding more sanctions.
Being a member of Igad (Inter-Governmental Authority on Development) would give it more diplomatic clout to resist moves to tighten measures.
Last week, the UN accused Eritrea of plotting to bomb January's African Union summit in the Ethiopian capital, Addis Ababa - an accusation it denies.
It also rejects charges that it has smuggled weapons to al-Shabab, an Islamist insurgent group which controls most of southern and central Somalia and has links to al-Qaeda.
Mr Maalim told the BBC's Focus on Africa programme that it was up to member states whether to readmit Eritrea and said the decision would have to be taken at the "highest level".
Igad is currently chaired by Ethiopia, which remains Eritrea's bitter foe after their 1998-2000 border war.
He also pointed out that the "serious allegations" against Eritrea would have to be taken into consideration.
He had earlier been quoted by the Reuters news agency as telling Eritrea's Foreign Minister, Osman Saleh, in a letter that he welcomed the country's "bold decision".
"I am confident that the Igad member states, the Igad development partners and all Igad stakeholders will be delighted to see Eritrea back in the Igad family fold," he said.
Eritrea gained independence from Ethiopia in 1993, but the two countries soon fell out and fought a war over their disputed border.
Eritrea accuses the West of not putting sufficient pressure on Ethiopia, an ally of the US, to respect an international commission's finding that it should withdraw from the town of Badme, which sparked the war.
It pulled out of Igad in 2007 after the body - made up of Kenya, Uganda, Djibouti, Ethiopia, Sudan and Somalia - backed Ethiopia's intervention to oust an Islamist precursor of al-Shabab from power in Mogadishu.
Eritrea has also cut links with international aid agencies and denies UN reports that it is suffering from the drought which has hit East Africa.