Analysts say the US policy towards Africa has strings attached, while China has not placed any such conditions.
Lavrov's visit to Africa coincides with the first visit to the continent by US Secretary of State Rex Tillerson.
"With the visit of Secretary of State Tillerson, the relation between Africa and the U.S. is personified,"Mahamat said, adding that the spat was "a thing of the past".
On Wednesday, he flew to Ethiopia at the start of his first diplomatic trip to the continent.
Tillerson's African tour, which will also include Djibouti, Kenya, Chad and Nigeria, is taking place after pejorative statements by U.S. President Donald Trump raised indignation among leaders of the continent.
Tillerson said Chinese investments "do not bring significant job creation locally" and criticized how Beijing structures loans to African government. Meanwhile, China announced on Monday that it expects to increase its foreign affairs budget by 15% from last year to a total of $9.5 billion - more than doubling what it was five years ago, according to the Financial Times.
The top American and Russian diplomats paid official visits this week to Addis Ababa, but don't appear to have met.
The complex was fully funded and built by China and is seen as a symbol of Beijing's thrust for influence and access to the continent's natural resources.
The former Exxon chief executive said China used corruption and predatory loan practices to undermine African governments and mire them in debt. "I want to add I am satisfied with the discussions I had with the secretary of state, notably the engagement of the United States to support Africa in the battle against terrorism". The Secretary commended the Prime Minister for his commitment to Ethiopia's future, demonstrated by his decision to step down, to facilitate a peaceful transition, and to make way for further reforms.
The emergency rule was aimed at restoring peace and security in the country.
On North Korea, Tillerson stated that African states must "take an active role" to combat global problems, not just solve local ones.
"This is something that Africa is still digesting", an Ethiopian journalist told Tillerson, asking whether he agreed or whether Trump owed Africans an apology.
Tillerson is due to fly to Djibouti, host to military bases owned by the U.S., China, Japan, France, and Italy.
Mahamat, in his remarks, said his discussions with the US envoy was fruitful, noting the visit was taking place at a time when Africa was firmly embarking on the path to integration and reform. "We know where our interests' lies and it is our full awareness I think that is most important", he said.