Federal troops are advancing on the Tigrayan capital Mekelle but Tigray's local leaders - who have a long history of guerrilla warfare - have vowed to fight.
Here are details on who has influence in Ethiopia and whether they are using it.
AFRICAN UNION - The African Union has appointed three former presidents to act as envoys to the crisis, but within hours of the announcement the Ethiopian government dismissed the possibility of mediation.
Government spokesman Redwan Hussein on Monday said Prime Minister Abiy Ahmed would meet the envoys and all options were on the table except negotiating with the Tigray People's Liberation Front (TPLF) "gang."
The AU fired its own security chief, an ethnic Tigrayan, after the Ethiopian government raised concerns over his loyalty.
SUDAN - The sliver of territory next to Sudan is Tigray’s only border not controlled by hostile forces; this border was vital to Tigrayan forces in a previous conflict. Sudan is also hosting nearly 40,000 refugees fleeing the conflict.
Regional experts have suggested that Sudan could use its control over key border crossings as leverage to press both sides in Ethiopia to talk. But so far there are no public signs it is doing so.
Cash-strapped Sudan is struggling to end a number of insurgencies on its own territory and manage a complex civilian-military government after overthrowing a long-standing dictator.
Sudanese transitional authorities have held talks with both Ethiopian and Eritrean officials since the fighting started. They have appealed for restraint, peaceful negotiations as soon as possible, and regional mediation.
CHINA - Beijing was a major lender to Addis Ababa as the government spent heavily on infrastructure in the decade before Abiy came to power. Last year, China canceled interest-free loans as the government struggled with its debt burden, though neither governments released details.
Beijing tends not to get involved in the internal affairs of countries it supports even with large public and private sector investments.
On Nov. 11, China's new ambassador to Ethiopia presented his credentials to Redwan Hussein, state foreign affairs minister and also the main government spokesman on its military campaign in Tigray.
The Ethiopian foreign ministry said Redwan "commended China for understanding Ethiopia’s stance not to internationalize the undergoing operation in Tigray ... The Chinese ambassador reaffirmed that China understands external power involvement in the Ethiopian government operation in Tigray is unnecessary since Ethiopia is capable of solving its own problems."
UNITED ARAB EMIRATES - Less than three months after Abiy took office, the United Arab Emirates pledged a total of $3 billion in aid and investment to Ethiopia, $1 billion of it as a deposit in the country's central bank to ease a severe foreign currency shortage.
The UAE, which has a military base at the Eritrean port of Assab, played a quiet but important role in the 2018 peace agreement between Ethiopia and Eritrea, part of the oil-rich Gulf state's push into the Horn of Africa over the past decade. In his first year in office, Abiy consulted regularly with Abu Dhabi's crown prince, Sheikh Mohammed bin Zayed, diplomats told Reuters at the time.
On Sunday, Foreign Minister Abdullah bin Zayed expressed his concern "over recent developments in Ethiopia" but also noted the importance of "non-interference in internal affairs," saying the UAE was making contacts around Africa and the world to try to end the conflict.
UNITED STATES - The current US administration may have lost leverage with Ethiopia, a traditional ally, by criticizing it over the filling of the Great Ethiopian Renaissance Dam.
Sudan and Egypt are concerned that the dam will restrict their access to Nile river waters. Ethiopia summoned the US ambassador to seek clarification after President Donald Trump said Cairo could end up "blowing up that dam."
The United States has condemned a rocket attack carried out by Tigrayan forces on an airport in Eritrea's capital Asmara.
Antony Blinken, due to become secretary of state under US President-elect Joe Biden, has urged the combatants to stop fighting and provide humanitarian access to protect civilians.
Blinken served as deputy national security adviser under former US president Barack Obama alongside officials including former UN ambassador Susan Rice and USAID chief Gayle Smith who are both known to have had close ties to former TPLF leader and Prime Minister Meles Zenawi.
UGANDA - President Yoweri Museveni, the region's longest-serving ruler, hosted a delegation from Ethiopia but Addis Ababa quickly clarified that they were there to explain an internal matter rather than seek guidance. Museveni later deleted his tweet calling for a halt to the conflict.
EUROPE - European countries have sought to lobby quietly for a de-escalation, without noticeable effect. The European Union, a major aid donor, publicly urged restraint and compliance with international law, saying it was deeply worried by "ethnically targeted measures, hate speech and allegations of atrocities."In a rare comment on activities of a laureate, the committee in Oslo that awarded the Nobel Peace Prize to Abiy said on Nov. 17 it was deeply concerned about the conflict and called on all parties to end violence. Abiy took the award in 2019 for making peace with Eritrea after a devastating 1998-2000 war and then lengthy standoff on the border.