SAO PAULO, June 11 (Reuters) - Brazilian chemical company Unipar Carbocloro has made a non-binding offer to conglomerate Novonor for the indirect acquisition of a controlling stake in petrochemical firm Braskem, according to a securities filing sent Saturday night.

Unipar proposed the partial payment of debt to five creditor banks that hold shares as guarantees and a renegotiation of the remaining debt owed by Braskem, in which Novonor and state-run oil firm Petrobras are the main shareholders.

The Unipar proposal also includes the possibility of Novonor, formerly known as Odebrecht, continuing with an indirect minority stake in Braskem, the filing said.

Valor Economico financial newspaper estimated that the offer is worth 10 billion reais ($2.05 billion), depending on the haircut creditors agree to take.

It said talks will take place this week with the banks, naming Bradesco, Itau Unibanco, Santander , Banco do Brasil and the National Development Bank BNDES.

Unipar will make a public offer for the acquisition of common shares and class A and class B preferred shares held by minority shareholders of Braskem and make a tender offer for up to all the class A preferred shares represented by American depositary receipts (ADRs) listed on the New York Stock Exchange.

Unipar said it will negotiate Petrobras' participation in the new share structure "at the right time" so as to seek a satisfactory format for all parties involved.

"Our proposal provides for a balance between the interests and needs of Novonor, Petrobras, minority shareholders and creditor banks of Braskem," Bruno Uchino, Unipar's board chairman, said in a press release.

Unipar is a leading producer of chlorine and soda and the second-largest producer of PVC in South America, it said. ($1 = 4.8791 reais) (Reporting by Leticia Fucuchima and Anthony Boadle; editing by Paul Simao and Marguerita Choy)