(Releads, adds union statement, detail and background)
By Giancarlo Navach and Oleg Vukmanovic
MILAN, July 18 (Reuters) - A one-day strike will shut all of oil and gas group Eni SpA's Italian operations on July 29 to protest at management plans to permanently close or convert some of the company's unprofitable refineries, labour unions said on Friday.
The 30,000-strong strike will include most of Eni's Italian staff and will lead to the shutdown of refineries, petrochemical and other production activities, as well as commercial, administrative and other offices, the statement said.
The escalating stand-off between unions and Eni will likely cast a shadow over the unveiling of new CEO Claudio Descalzi's strategy presentation on July 31.
Industry sources say Descalzi is readying a plan to shed loss-making business lines, such as the company's Italian refineries, and strengthen Eni's push into more profitable oil and gas exploration activities.
For other non-Eni operated refineries, the strike is expected to last only two hours, the statement said.
On the day of the strike, unions plan to stage a national demonstration in Rome at 3 p.m. (1600 GMT).
Worker protests at Italian companies are mounting in the face of record high unemployment levels, as the country struggles to emerge from its longest recession in 70 years.
Union bosses have told Reuters that Eni's plans to restructure its domestic refining business could lead to the loss of up to 6,000 jobs and the permanent closure of sites at Gela, Taranto, Livorno, Porto Marghera and Priolo.
Eni's loss-making refining business is the Achilles' heel of the state-controlled group and Eni could suffer a credit rating downgrade if it fails to turn it around, Fitch Ratings warned last week. (Reporting by Giancarlo Navach and Oleg Vukmanovic; Editing by David Holmes)