SAO PAULO (Reuters) -Brazilian businessman Nelson Tanure may give up on his bid to acquire a controlling stake in Latin America's largest petrochemical firm Braskem as his exclusive negotiations window nears closing without an agreement to resolve claims from an environmental incident linked to the company.

Last May, Tanure signed a 90-day exclusivity document to discuss the terms of an offer to acquire a controlling stake in Braskem from Novonor, formerly Odebrecht. The businessman has since been working to resolve issues stemming from environmental investigation into ground subsidence in the northeastern city of Maceió, where Braskem had rock salt mines.

In a written response to Reuters on Monday, Tanure said settling this case is a non-negotiable term for his Braskem bid, whose current exclusivity period ends on August 21.

"An agreement with all entities involved in the Alagoas disaster is a sine qua non (condition), and especially applies to the non-transfer of criminal and financial responsibility to the new shareholders," he answered without elaborating on his next steps.

The incident was allegedly caused by Braskem's rock salt extraction activities, which began in the 1970s and were halted in 2019 after authorities determined they contributed to the sinking of five neighborhoods, leading to the displacement of thousands of residents.

As Tanure mulls his next moves, private equity firm IG4 Capital is biding its time, poised to launch a rival bid when Tanure-Novonor agreement lapses. IG4's strategy aims to consolidate Novonor's bank debt and exchange it for Braskem shares, sources said.

Braskem, Novonor and IG4 all declined to comment .

The critical decision period coincides with Brazil's Unipar's reported attempt to purchase Braskem's U.S. polypropylene plants for about $1 billion. Made public last week, the bid lacks approval from key parties, including Tanure and IG4, according to sources.