DUBAI, July 16 (Reuters) - Abu Dhabi National Oil Company said on Wednesday it plans to transfer its 24.9% shareholding in Austria's OMV AG OMVV.VI to its XRG investment unit ahead of the establishment of a chemicals company combining existing OMV and ADNOC firms.

ADNOC last year bought a 24.9% stake in OMV from Abu Dhabi sovereign wealth fund Mubadala, without disclosing the financial terms.

Earlier this year, ADNOC and OMV agreed to merge their polyolefin businesses to create a chemicals company with a $60 billion enterprise value.

The merged entity, Borouge Group International $(BGI)$, is set to be the world's fourth-largest polyolefins firm by production capacity, behind China's Sinopec and CNPC and U.S.-based ExxonMobil XOM.N, ADNOC Downstream CEO Khaled Salmeen told Reuters in March.

BGI will combine two joint ventures - Borealis, 75% owned by OMV and 25% by ADNOC, and Borouge BOROUGE.AD, 54% owned by ADNOC and 36% by Borealis, the company announced in March.

In its statement on Wednesday, ADNOC said it is progressing with preparation for the proposed establishment of BGI.

ADNOC's proposed 46.94% shareholding in BGI is expected to be held by XRG upon completion of the transaction, subject to regulatory approvals, the statement said.

(Reporting by Hadeel Al Sayegh; Editing by Christian Schmollinger)

((Hadeel.AlSayegh@thomsonreuters.com; +971566883310;))