The commander of the rebel group in Ethiopia's northern region of Tigray has told the BBC they will continue fighting until their terms for a ceasefire are met.
Gen Tsadkan Gebretensae said the group aims to force the federal government to lift a blockade in the region and agree to a political solution to the crisis.
The government has not reacted to the rebel's conditions.
Thousands have been killed since war broke out in November last year.
Millions of people have also been displaced by the fighting which both sides have been accused of committing human rights abuses and war crimes.
At least 400,000 people are living in famine conditions, according to a UN estimate, with access to the region still being hampered. UN World Food Programme lorries did manage to reach Tigray at the weekend after a long delay because of security concerns.
Despite the government announcing a unilateral ceasefire in June after the rebels made significant gains, including the recapture of the region's capital, Mekelle, it has continued to mobilise militia from other parts of the country to help stall the rebels' advance in neighbouring Afar and Amhara regions.
Gen Tsadkan, a former head of the Ethiopian army, told the BBC Newshour programme that his fighters' incursion to the neighbouring regions was aimed at removing a federal blockade that has prevented aid from coming through.
He said that before a ceasefire is agreed the federal government had to:
stop the persecution of Tigrayans
release political prisoners
accept an inclusive dialogue to determine the region's future.
He said the war could have been avoided, and accused Prime Minister Abiy Ahmed of not willing to find a peaceful solution to the political standoff between the federal government and the Tigray People's Liberation Front (TPLF).
"I regret that this has happened, I regret that this could have been avoided, but I'm happy that the Tigray people fought and are in a position to demand their rightful position in the region," Gen Tsadkan said.
The Ethiopian government, which has designated the TPLF as a terrorist organisation, has not reacted to the general's comments.
The TPLF was Tigray's governing party until it was ousted by the national army in November last year but the rebels say they are the legitimate regional government of Tigray.
Its leaders fell out with the Mr Abiy over his political reforms, though the TPLF's capture of federal military bases in Tigray was the catalyst for the invasion.