Prime Minister Shaukat Aziz Tuesday left for Tehran on a three-day visit to Iran, officials said. 'Iran is the most important neighbour of Pakistan. I will be discussing with Iranian leadership gas pipeline project besides bilateral, regional and international matters of mutual interests' the prime minister told the reporters before departing for Tehran. Aziz said Pakistan has three options for gas pipeline, which include Turkmanistan- Afghanistan-Pakistan; Iran-Pakistan-India and Qatar-Pakistan-India gas pipelines projects. The prime minister said Pakistan was discussing all the three options and any one of them found most viable economically would be taken up. Aziz said that a 25-year energy programme has been prepared for meeting the energy requirements of Pakistan and the possibility of obtaining natural gas from the Gulf countries was also under consideration. The prime minister said the supply of electricity from Iran to the bordering areas of Pakistan was also included in the agenda for talks with the Iranian leadership during his visit. Aziz said Pakistan is already buying electricity from Iran for some areas of its Balochistan province and is eager to obtain power for Gawadar as well. The agreements to be signed during Aziz's visit include joint investments in fruits and transport sectors and drug control measures.