Nine anti-government factions in Ethiopia are to form an alliance, as pressure mounts on the country’s prime minister, Abiy Ahmed, with rebel forces advancing toward the capital.

The alliance, called the United Front of Ethiopian Federalist and Confederalist Forces, includes the Tigray People’s Liberation Front (TPLF), which has been fighting Abiy’s government for a year in a war that has killed thousands of people and forced more than 2 million more from their homes.

Two of the groups, the Oromo Liberation Army (OLA) and the Agaw Democratic Movement (ADM), confirmed the announcement was genuine.

Several of the groups have armed fighters although it was not clear whether they all do.

Abiy’s spokesperson, Billene Seyoum, when asked about the new anti-government alliance, referred to a comment she posted on Twitter in which she defended Abiy’s rule since he took office in 2018 after a wave of anti-government protests. His party was re-elected in June.

“The opening up of the political space three years ago provided ample opportunity for contenders to settle their differences at the ballot box in June 2021,” Seyoum said in the post.

She did not refer directly to the new alliance.

Spokespeople for the government and the foreign ministry did not respond to requests for comment on the alliance.

African and western nations are calling for an immediate ceasefire in Ethiopia after Tigrayan forces from the north said they made advances towards the capital this week.

The US secretary of state, Antony Blinken, said in a tweet late on Thursday: “The conflict in Ethiopia must come to an end. Peace negotiations should begin immediately without preconditions in pursuit of a ceasefire.”

The spokespeople for the Ethiopian government and the TPLF did not respond to requests for comment on Blinken’s ceasefire call.

US senators on Thursday introduced a new sanctions bill on parties to the conflict in Ethiopia.

“This is a regional crisis that requires a coordinated and intensive international response,” said Senator Jim Risch, a Republican from Idaho.

The announcement of the alliance comes during a two-day visit to Addis Ababa by the US special envoy to the Horn of Africa, Jeffrey Feltman.

On Thursday, he met the African Union Commission chairperson, Moussa Faki, as well as the Ethiopian defence minister, finance minister and deputy prime minister, according to the State Department.

It was not clear whether the US envoy would meet Abiy.

The TPLF spokesperson, Getachew Reda, did not respond to comment requests on Friday.

The groups will hold a signing ceremony on Friday in Washington, they said in the announcement.

The front is being formed “to reverse the harmful effects of the Abiy Ahmed rule on the peoples of Ethiopia and beyond”, the groups said. It is also being formed “in recognition of the great need to collaborate and join forces towards a safe transition in the country”.