'Once the work begins, the tunnel needs minimum five years to get completed. Since all topographical surveys have been completed, now only green signal from the government is awaited,' Mathur added.

Himachal's PWD Minister Gulab Singh Thakur said the state government attaches great importance to the Rohtang tunnel project.

'The project is strategically important to the defence forces as well as to boost economic development in the Lahaul-Spiti region. We have been in regular touch with the BRO to see that the project starts as early as possible,' he said.

Latest estimates show the tunnel, billed as the longest highway tunnel so far in the country, needs Rs.1,700 crore to get completed.

'The horse-shoe shaped tunnel would cost approximately Rs.1,700 crore. Its construction would be a Herculean task as the temperature at the site varies from 25 to 30 degrees Celsius during May-June and minus 20 to minus 2 degrees Celsius during December-January. The area sees heavy snow and high velocity winds,' Mathur said.

The Manali-Leh highway winds its way through the Rohtang Pass, Baralacha Pass (16,020 ft), Lachlungla Pass (16,620 ft) and Tanglangla (17,480 ft).

The highway plays an important role in the movement of the armed forces to the forward areas in Ladakh.