Pep Guardiola's side piled the pressure on in the first half of the first leg at Red Bull Arena and Riyad Mahrez fired City into a deserved 27th-minute lead on Thursday (AEDT).

But City's control wavered in the second period as substitute Benjamin Henrichs missed two great chances before Gvardiol earned a share of the spoils with a thumping header after 70 minutes.

Guardiola will be left rueing what could have been after an impressive display in the opening half, leaving it all to play for in the March 14 return leg at Etihad Stadium.

City monopolised possession in the opening stages but created little without absent chief creator Kevin De Bruyne, who missed the Germany trip through illness.

That pressure soon told, though, as Ilkay Gundogan punished a wayward Xaver Schlager pass to find Mahrez, who arrowed into the bottom-right corner from outside the area.

Rodri headed narrowly wide and Jack Grealish blazed over as City threatened to further their advantage, with Leipzig fortunate to go in at half-time just a goal down.

Henrichs should have levelled after the interval, first wastefully heading over before dragging a glorious opportunity wide to the right of Ederson, who denied a fizzing Dominik Szoboszlai strike soon after.

The much-improved Leipzig grabbed a deserved equaliser from Marcel Halstenberg's resulting corner as Gvardiol powered home, with City's appeals for a foul falling on deaf ears.

Janis Blaswich then denied a whipped Gundogan effort destined for the bottom-right corner, ensuring it remains all to play for in the return leg in England.