The United States has pledged over $1 billion in aid to Mali since the election of President Ibrahim Boubacar Keita
The U.S. ambassador to Mali has accused the government of maintaining relations with a militia widely blamed for rising tensions that risk undermining a fragile peace process in the country's desert north.
His comments were the latest indication that key donors to the West African state are taking a harder line towards the government, which denies all ties to Gatia - a mostly Tuareg militia opposed to pro-independence fighters in the north.
"The Malian government should put a stop to all ties both public and private with Gatia, a group of armed militia that is not contributing to peace in the north," Paul Folmsbee said in a post on the U.S. Embassy's Facebook page on Wednesday.
"Mali needs to assume a greater responsibility for the peace deal's implementation," he said, urging the southern-based Bamako government to step up its presence throughout the sprawling country.
A government spokesman declined to comment on the allegation of ties to Gatia. Folmsbee did not give details of whether the ties were financial or military.
The United States has pledged more than $1 billion in aid to Mali since the election of President Ibrahim Boubacar Keita in 2013 after a period of instability.
In a statement, Gatia did not directly deny any links to the Bamako government but said its mission was to protect an ethnic group within the Tuareg known as the Imghad, not to act as an arm of the authorities in northern Mali.
"(Gatia) was created ... to protect the Imghad people and their allies who have been abandoned by the state in an area where there are armed groups that kill and humiliate with impunity," Gatia's deputy secretary-general Habala Hamzata said in the statement.
Security has been deteriorating in Mali for months despite a peace deal signed in June 2015 between the government and a medley of mostly Tuareg secular armed groups based in the desert north.
The deal was seen as an important precursor to striking at al Qaeda-linked militants based in the same region and who briefly seized key northern cities in 2012.
Many of the rivalries between fighters from the Tuareg minority ethnic group date back centuries and are linked to control of desert trade routes. Up to 20 died in fighting in remote locations in July and there have been further clashes near the northern town of Kidal in recent weeks.
The U.S. ambassador to the United Nations, Samantha Power, made similar allegations against the Malian government last week during a session on Mali in New York.