“I want to get back to my national team,” Niang said in Johannesburg on Wednesday evening.
“I think Sundowns will help me to achieve my goal.”
Niang was earlier linked to a move to Orlando Pirates but he said Sundowns’ offer was too good to refuse.
“I had other options on the table. As you know Pirates showed interest and even Bloemfontein Celtic, but I think Sundowns was the best decision for me.”
The 30-year-old officially completed his transfer from SuperSport United to the Brazilians late on Wednesday. In return United signed Sundowns’ striker Dove Wome on a one-year loan.
Niang signed a three-year deal with the defending champions and is set to join the squad that was in pre-season camp in Cape Town.
The 2005/2006 PSL top goal scorer said he was also lured by the prospect of playing in the Caf Champions League, a continental tournament Sundowns qualified for as Premiership champions.
“I have played in the Champions League before and I got to the quarter-finals with one of my previous teams (ASC Diaraf),” Niang said.
“I am used to it and it was one of the major reasons I joined Sundowns.”
Niang could make his debut for his new side as soon as Friday in the Cape Town Football Challenge, a pre-season tournament that includes Wits, Ajax Cape Town and Chippa United.