The Delhi Metro Rail Corporation had initially planned to throw open the remaining section of the 9 km-long metro corridor, whose Mandi House-ITO part is operational, by October and had later advanced the deadline to August.
Constructing the completely underground corridor has been extremely challenging as the area above is densely populated areas, including those in old Delhi, officials said.
"DMRC has overcome all the technical challenges and aims to complete this line by August 2016 and trial runs will start in August itself.
The Mandi House-ITO section was launched on June 8 last year. The section derives its heritage value from the fact that it passes under areas of the walled city such as Delhi Gate, Jama Masjid and Red Fort.