(Recasts with reaction from Grana y Montero)
LIMA, Nov 23 (Reuters) - Sempra Energy said Wednesday that it dropped its offer to buy a stake in Odebrecht SA's natural gas pipeline concession in Peru, leaving junior partners scrambling to try to save the project as the government eyes a new auction.
Sempra gave up on months of negotiations after the government refused to strip an anti-corruption clause from the contract that would let it seize the project if Odebrecht were found to have broken any laws.
"A fundamental condition...was not satisfied," Sempra said in a statement.
Odebrecht, a family-owned Brazilian engineering conglomerate that controls 55 percent of the project, is at the center of Brazil's biggest graft scandal. Prosecutors in Peru have been probing potential wrongdoing in the awarding of the pipeline contract.
Sempra's announcement was the latest setback for Odebrecht as it faces some $2.1 billion in fines in Brazil and is seeking to sell its assets to pay its bloated debt.
It also clouded the plans of Odebrecht's junior partners on the project, Peruvian builder Grana y Montero and Spanish energy company Enagas SA.
Financing for the pipeline's construction hinges on Odebrecht's full departure from the project as a group of banks have made that a condition to disbursing a $4.1 billion loan.
The government of President Pedro Pablo Kuczynski, eager to push out stalled infrastructure projects to boost slumping domestic demand, has said it could hold a new auction for the project next year if Odebrecht does not sell its stake soon.
Grana, which bought its 20 percent stake in the pipeline project for $215 million in 2015, said it was working on "alternatives" to keep the project alive together with Enagas and Italian Techint Group.
Enagas controls a 25 percent stake in the pipeline project and Techint wants to buy a 5 percent stake from Odebrecht. "For Techint nothing has changed," the company said in an email.
If the government rescinded the contract, Grana would recover its investment thanks to a termination payment clause, it said. The company's shares on the Lima bourse have dropped about 20 percent this week.
The government said it would probably modify the contract so it is not financed through consumer electricity bills.
Odebrecht won the rights to build and operate the pipeline in 2014 after its sole competitor - a Sempra-led group - was disqualified the day of the auction for making last-minute changes to the stake each company held in the consortium.
Reporting by Mitra Taj and Marco Aquino; Editing by Grant McCool and Lisa Shumaker