Each line of the expansion programme, which will add 56 kilometres to the existing network, is estimated to cost up to $1,000 million, industry sources say. Bidders will need to submit their own financing proposals.

Mohsen Hashemi Bahramani, chairman and managing director of the Tehran Urban & Suburban Railway Company (TUSRC),was quoted on 10 October as saying that the project would require financing for 'the construction of new tunnels and stations and the purchase and installation of rolling stock, high- and low-pressure energy systems, a control and signalling system, workshops and an automatic fare collection system'.

According to TUSRC, at least 51 per cent of the total works of the scheme will need to be carried out by local firms. International companies are expected to provide the bulk of the required technical equipment and trains.

It is understood that the local Jahanparsis holding negotiations with Germany's Siemensand several other companies to form a consortium for the scheme. Other international companies likely to be interested in the project are France's Alstomand Chinese firms such as CITIC, which provided the bulk of the technical equipment for the metro's line 2.

Line 3 will add 37 kilometres to the existing network, while line 4 will see a 19-kilometre extension.