An Ethiopian rebel group declared a unilateral ceasefire on Sunday, the latest dissident movement to aim for an end to hostilities in the wake of reforms.
The Ogaden National Liberation Front (ONLF) launched its bid for secession of the Somali Region, also known as Ogaden, in eastern Ethiopia in 1984.
In 2007, Ethiopian forces waged a large-scale offensive against them after the group attacked a Chinese-run oil facility, killing 74 people.
But the ONLF was among two other groups that were removed by parliament from a list of banned movements - part of a reform drive being led by Prime Minister Abiy Ahmed, who has extended an olive branch to dissidents.
In a statement, the ONLF said it had "taken into account the positive steps taken by the Ethiopian government to lay the groundwork for talks and peaceful negotiations".
The group "will cease all military and security operations to find a available and lasting solution to the Ogaden conflict", it added.
The region the ONLF operates in contains four trillion cubic feet of gas and oil deposits, the government says. China's GCL-Poly Petroleum Investments has been developing two gas fields since 2013.
Abiy, who took office in April, is presiding over a bold push to shake the African nation of 100 million people from decades of security-obsessed rule.
He has also acknowledged and condemned widespread abuses by security forces, likening it to state terrorism, as well as forging peace with Eritrea, with which Addis Ababa has been locked in a lengthy military standoff that followed a 1998-2000 border war in which 80,000 people are thought to have died.