A spokesman for the Tigrayan forces did not respond to a request for comment on the announcement, which follows a visit by the US Special Envoy for the Horn of Africa, David Satterfield, to the capital Addis Ababa this week.
More than 90 per cent of 5.5 million Tigrayans need food aid, the United Nations says, but only a tiny trickle has entered since Ethiopian troops withdrew from Tigray at the end of June last year.
The 16-month-old conflict has pitted Tigray's rulers - the Tigray People's Liberation Front - against the central government led by Prime Minister Abiy Ahmed.
"The government of Ethiopia hopes that this truce will substantially improve the humanitarian situation on the ground and pave the way for the resolution of the conflict in the northern Ethiopia without further bloodshed," the government said in a statement.
Government spokesman Legesse Tulu told Reuters the truce was unilateral.
"This is just a government decision to protect our citizens from danger," he said.
"We hope the other side (TPLF) will do the same."
Tigrayan leaders have blamed central and regional authorities for blocking aid into Tigray.
The central government has said Tigrayan fighters have blocked the aid because they have invaded Afar, a neighbouring region along the only land route currently open into Tigray.
The United Nations humanitarian arm OCHA said no trucks have made it into Tigray since December 15, citing administrative as well as security constraints.
OCHA said the aid effort is hampered by a lack of funds, supplies and partners.
This week a UN convoy that tried to reach several towns under government control in Afar was stoned, the drivers beaten and the food stolen, according to three aid workers.
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