The Karachaganak Petroleum Operating Group (KPO) has started talks on Kazakhstan taking a stake in the oil and gas consortium, Italy's Il Sole 24 Ore reported.
Kazakhstan has long sought a stake in the giant Karachaganak oil and gas field in the west of the Central Asian country. KPO is led by Italy's Eni SpA and Britain's BG Group Plc, each with 32.5 percent.
Talks have started in London "but are showing themselves to be more and more difficult," the business daily said, citing sources close to the issue.
BG is more resistant to the Kazakh move since it would mean the British company reducing its stake, Il Sole 24 Ore said.
Eni had no immediate comment. KPO also includes Russia's LUKOIL and U.S. major Chevron Corp.
Kazakhstan accused KPO this month of violating immigration laws, stepping up pressure as it seeks a stake in the field.
In March, Kazakhstan's financial police accused Karachaganak of illegally earning $708 million (460 million pound) in 2008 by producing more oil and gas than originally agreed with the state.
The group has denied any wrongdoing.
