Iran's Petroleum Minister says it plans to introduce by June a new generation of oil contracts that are more attractive to investors. Mahdi Hosseini, head of the contract revision committee in the ministry, told reporters Sunday that sanctions imposed on Iran over its nuclear activities drove the revisions. He said the new contracts are designed for the "post-sanction era, " but did not provide details. So far Iran has allowed oil companies to work on its fields under contracts known as "buybacks." Hosseini said many companies complained about their costs under this scheme. Iran signed in November a six-month interim deal with world powers in which it stops some nuclear activities in return for sanctions relief. It begins negotiations this month to reach a final deal.