The Cranes are yet to lose a match in this campaign after beating Cape Verde 1-0 away, before drawing 0-0 with Tanzania at home last month. Lesotho are on second place with two points.
“We are ready to try our best in the game,” Onyango said at Friday’s press conference.
“Lesotho are not a small team. In football there is no small team. They have not lost any game in the campaign.”
After Saturday’s match, Uganda travel to Lesotho for the return fixture on Tuesday.
The Cranes' Sebastien Desabre is enjoying a clean bill of health in his camp with no injury concerns.
“We want to go to Maseru with positive results. Everyone is ready. With the support of the nation (fans and media), we need to lift the team,” Onyango said.
“There are no injuries at the moment in the camp. Everyone is in shape and we shall give our best. The advantage is that we are at home, we have to play our hearts out during the first leg. It is one game at a time. We believe we shall make it to the next stage.”
Onyango captained Uganda at the 2017 Afcon finals, and he is hoping to do the same in Cameroon.