Iraq and oil major BP have signed a deal to redevelop four Kirkuk oil and gas fields, BP said on Tuesday, a breakthrough for Iraq, where output has been constrained by years of war, corruption and sectarian tensions.

BP's (NYSE:BP) deal to redevelop oil and gas fields in Iraq's Kirkuk region eventually will be viewed as of the company's most important transactions in 20 years, CEO Murray Auchincloss said Wednesday during the launch of its anticipated strategic reset.

BP Plc finalized an agreement with the government of Iraq to redevelop the giant Kirkuk oil fields, a deal that signals a return to the company’s Middle Eastern routes and should help to bolster production from the OPEC member.

Government of the Republic of Iraq to invest in several giant oil fields in Kirkuk providing for the rehabilitation and redevelopment of the fields, spanning oil, gas, power and water with potential for investment in exploration.

The state-owned North Oil Company (NOC) and British Petroleum (BP) signed on Tuesday an agreement to develop four oil fields in Kirkuk.

BP will redevelop 3 billion barrels of oil equivalent across five fields in Iraq, all of which are currently operated by state-owned North Oil Company.

Oil major BP is expected to spend up to $25 billion over the lifetime of a project to redevelop four Kirkuk oil and gas fields, a senior Iraqi oil official told Reuters, as Baghdad seeks to win back foreign investment.

BP had stalled plans for years citing risks of political instability in the province claimed by Iraq’s autonomous region of Kurdistan. In 2013 BP signed a deal with the Iraqi government “on providing technical assistance relating to the Kirkuk oil field”, according to the company’s annual report for that year.

British energy giant BP signed an agreement with the Iraqi government on Tuesday to rehabilitate four oil and gas fields in Kirkuk province, just weeks after reaching an initial deal.

BP has signed a significant agreement with Iraq to redevelop four oil and gas fields in Kirkuk, aiming to increase production and support domestic energy needs. The project involves an investment of up to $25 billion and highlights a shift back to oil from renewables for BP.