Prime Minister Abiy Ahmed had declared a unilateral ceasefire in late June after TPLF forces retook the Tigrayan capital Mekele.
Ethiopia warned Friday it could deploy its "entire defensive capability" after advances by Tigrayan rebels into neighbouring regions.
The government "is being pushed to mobilise and deploy the entire defensive capability of the state if its humanitarian overtures for a peaceful resolution of the conflict remain unreciprocated," the foreign ministry said in a statement.
"The action of the irresponsible group is testing the federal government's patience and pushing it to change its defensive mood which has been taken for the sake of the unilateral humanitarian ceasefire."
Earlier Friday, the spokesman for the Tigray People's Liberation Front (TPLF) rebuffed calls to withdraw from the neighbouring Afar and Amhara regions.
The comments came a day after the rebels seized Lalibela, a UNESCO World Heritage Site in Amhara, the latest turn in the nine-month-old conflict.
Prime Minister Abiy Ahmed had declared a unilateral ceasefire in late June after TPLF forces retook the Tigrayan capital Mekele.
Top US officials have urged the TPLF to withdraw from the regions east and south of Tigray and called on all sides to cease hostilities and focus instead on addressing the humanitarian "catastrophe" in Tigray.