National Iranian Gas Export Company Managing Director, Reza Kasaeizadeh, said Tehran and Islamabad also signed agreement on a gas price formula.
About 1,100 kilometers of the pipeline would be in Iran, while other 1,000 kilometers would be covered by Pakistan.
Tehran says both Iran and Pakistan would welcome India if it resolute to join the project.
Nearly 600 kilometers of the pipeline will also run in India if the country joins the project.
Iran has already completed the main portion of the pipeline form Asalouyeh to Iranshahr (near Iran-Pakistan border) and some 250 kilometers of the project is remained unfinished, Kasaeizadeh said.
He expressed belief that the start of gas delivery would commence within three or four years after the contract was signed.
Kasaeizadeh says South Pars gas field will deliver gas to Pakistan through the under construction pipeline which is about 2100 kilometers.
