(CNN) The Biden administration has described a CNN report that Ethiopian Airlines shuttled weapons to Eritrea as "incredibly grave" and warned that it was prepared to impose sanctions on Ethiopia and any other parties who prolonged the conflict in Tigray.
On Wednesday CNN revealed that Ethiopia's government used its state-owned commercial carrier to move weapons to and from neighboring Eritrea during the first weeks of the conflict. It is the first time this weapons trade between the former foes has been documented during the nearly year-long war in Ethiopia's northern Tigray region.
Reacting to the investigation, a senior US administration official said: "These allegations are incredibly grave; not only could they constitute a potential violation of the Chicago Convention [on international civil aviation]. The use of civilian aircraft to ferry military hardware upends norms and endangers passenger craft around the world."
The official added that the US would not hold back from using all the tools at its disposal to put an end to a conflict that has triggered famine and left millions in desperate need of aid -- including the sanctioning of officials responsible for drawing out the conflict.
"We have the ability to impose sanctions and are prepared to use them and other tools at our disposal against those prolonging the tragedy in Tigray," the official said.
A separate senior administration official told CNN that the White House was looking into the allegations detailed in its report. "If true, they would be deeply concerning, as Ethiopia is seriously risking the reputation of its national airline by enlisting it in military operations that have unleashed one of the world's worst humanitarian crises," the source said.
The comments from the two officials come three weeks after President Joe Biden threatened to impose broad new sanctions on Ethiopian officials and other parties to the conflict, unless they stopped fighting and opened up humanitarian access. But the Ethiopian government has not yet taken meaningful steps toward de-escalating the conflict, administration officials have said.
Ethiopian Airlines told CNN it "strictly complies with all National, regional and International aviation related regulations" and that "to the best of its knowledge and its records, it has not transported any war armament in any of its routes by any of its Aircraft."
But CNN used cargo documents and manifests, as well as eyewitness accounts and photographic evidence, to establish that arms were transported between Addis Ababa's international airport and airports in the Eritrean cities of Asmara and Massawa on board multiple Ethiopian Airlines planes in November 2020.
The governments of Ethiopia and Eritrea did not respond to CNN's requests for comment.
In response to the latest CNN investigation, US Rep. Tom Malinowski, a Democrat from New Jersey, called for Ethiopia Airlines and its executives to be "held accountable," adding he would be in favor of individual sanctions against Ethiopian Airlines executives.
"If true, it's a very serious matter that goes well beyond our interest in ending the violence in Ethiopia," he said in an interview with CNN on Wednesday.
Malinowski added that the international rules that prohibit civilian airlines from carrying military equipment "are extremely important because if violated they expose, they make it more likely, that civilian aircraft will be fired upon in times of war."
"So this endangers everybody. It undermines the norm that protects everybody in the world who travels on international carriers," he continued.
"I think that the airline and potentially its executives should be held accountable," Malinowski said. "That may require fines to be imposed, it may require individual sanctions against Ethiopian Airlines executives. This is not a trivial matter and it needs to be dealt with by the Biden Administration swiftly and firmly."
Malinowski is leading an amendment to the National Defense Authorization Act (NDAA) pushing the administration to determine on whether genocide has occurred in Tigray. "I think even the passage of the legislation sends a strong signal to the Ethiopian and Eritrean governments that their grace period is coming to an end," he said.
CNN's investigation offers fresh insights into how Ethiopian Prime Minister Abiy Ahmed has coordinated his offensive in Tigray with the help of Eritrean President Isaias Afwerki -- a longtime enemy of Ethiopia until the two leaders signed a peace deal in 2018.
The war between Ethiopia's military and forces loyal to the TPLF, which controls Tigray, broke out in November 2020. Within weeks, Eritrean soldiers had reportedly crossed into Tigray to assist Ethiopian troops. Eleven months on, the fighting has left thousands dead, forced 2 million to flee, fueled famine and given rise to a wave of atrocities.
Though all sides have been accused by the UN of committing grave human rights abuses, previous CNN investigations have found that Eritrean soldiers have been behind among some of the worst abuses carried out in Tigray, including sexual violence and massacres. Eritrea has denied wrongdoing by its soldiers, and has refused to pull them out of the region despite multiple calls for their removal.
Abiy, who was sworn in for a second term as prime minister on Monday, has been condemned for his role in presiding over a protracted civil war that, by many accounts, bears the hallmarks of genocide.
International criticisms have been growing over the role of the Ethiopian government and its allies in restricting critical humanitarian aid in Tigray.
United Nations Secretary-General Antonio Guterres called for Addis Ababa to grant the UN "unhindered" aid access to the region during a Security Council meeting on Wednesday.
It was the second emergency council meeting in a week to discuss the government's expulsion of seven senior UN officials -- most of them humanitarian staff -- amid a worsening famine in Tigray. The UN estimates that the conflict has left more than 5 million people in need of food assistance and driven 400,000 into famine-like conditions, with increasing accounts of hunger-related deaths.
"The country is facing an immense humanitarian crisis that demands immediate attention. All efforts should be squarely focused on saving lives and avoiding a massive human tragedy," Guterres said, calling the Ethiopian government's decision "particularly disturbing."
Guterres demanded Ethiopian authorities allow the UN to deliver humanitarian assistance "without hindrance and to facilitate and enable our work with the urgency that this situation demands," and slammed the country for not following formal procedures.
"It is my duty to defend the honor of the United Nations," Guterres told reporters Wednesday after the council meeting concluded.
Ethiopia's ouster of the officials came just days after the UN's aid chief warned that hundreds of thousands of people were starving due to the government's blockade of aid deliveries.
Reacting to the news last week, White House press secretary Jen Psaki told reporters that the US condemned the expulsions and would not hold back from using sanctions against any group obstructing aid efforts.
"It must stop," Psaki said.