(Bloomberg) -- Brazil’s Braskem SA tumbled on Monday after Abu Dhabi National Oil Co. dropped its bid for a stake in the troubled Brazilian petrochemicals company, a development that signals the stop-and-start sales process will drag on even longer. 

Adnoc, the biggest oil producer in the United Arab Emirates, is walking away from its $2.1 billion offer, disappointing equity investors who were expecting a deal. Braskem shares fell as much as 16% in New York on the news and were on track for the lowest close since February.

Braskem’s financially strained controlling shareholder, Novonor SA, has been trying to sell its stake for years. Petrobras, Brazil’s state-controlled oil company and Braskem’s second-biggest shareholder, would like to see a new investor take over for Novonor, Chief Executive Officer Jean Paul Prates said in February. 

Demand for plastics, paints and car parts made from the petrochemicals that Braskem produces is expected to increase in the region, and Braskem’s facilities in Brazil and other countries can be built out if consumption grows. Still, it has been a challenge for Novonor to lock in a buyer for its stake.

“From our perspective, it’s too early to access why Adnoc would exit the sales process,” Citigroup Inc analysts led by Gabriel Barra wrote in a report.

In a statement, Braskem published the contents of a letter it received from Novonor related to Adnoc’s decision to pull out of the potential deal, which it had announced in November. Novonor said it remained fully engaged in the sale process, according to the correspondence. 

In March, Braskem said that a new bidder had entered the race for the stake, without specifying who. Braskem is the top maker of thermoplastic resins in the Americas, and a leading global producer in terms of capacity. 

Read More: Braskem Says There’s a New Potential Buyer for Novonor’s Stake

Adnoc looked at Braskem as part of a push to develop a global chemicals business and diversify beyond crude oil and refined products. It’s also pursuing other deals, including a proposed multibillion-dollar acquisition of German chemicals group Covestro AG and a separate merger of two plastics units that would create a business worth more than $30 billion.

So far those discussions have also run into hurdles. The company’s plan to merge Abu Dhabi-listed Borouge Plc with Borealis AG has been held up over valuation talks with partner OMV AG of Austria. Now coming elections in the European country threaten further delays. Covestro is in open-ended talks with Adnoc and may be waiting for a higher offer. 

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