Colombia"s financial regulator has approved a public acquisition offer by Grupo Gilinski for a minority stake in Grupo SURA (SIS.CN), Colombia"s largest holding company, a source close to the operation said late on Tuesday. The formal announcement of the offer will be published on Thursday and the offer will finish on Jan. 11, the person said. The offer is seeking between 25.34% and 31.68% of Grupo SURA shares, valued at up to $1.19 billion. Both SURA and the financial regulator said they had no comment. SURA said late on Monday it will not participate in a separate public acquisition offer from Gilinski for food producer Grupo Nutresa SA (NCH.CN), as the deadline for the sale was extended. Grupo Gilinski and Abu Dhabi"s Royal Group want to buy between 50.1% and 62.625% of circulating shares in Nutresa for up to $2.2 billion via their joint NUGIL S.A.S. vehicle. "The board of Grupo SURA, after various sessions in which only independent members participated, has unanimously determined not to accept the public offer for acquisition of shares in Grupo Nutresa presented by Nugil S.A.S.," Grupo SURA said in a statement late on Monday. Grupo SURA holds 35.7% of Nutresa"s shares. Grupo Argos SA (ARG.CN), which holds about 10% of Nutresa shares, has also said it will not participate in the offer. read more "For Grupo SURA, the offer is significantly removed from the value of Grupo Nutresa and its portfolio of investments," the statement added, citing a financial assessment conducted by Bank of America. NUGIL said on its website it would extend the offer period - initially set to end on Friday - until Jan. 12. Reporting by Nelson Bocanegra; Writing by Julia Symmes Cobb; Editing by Will Dunham and Sonya Hepinstall Our Standards: The Thomson Reuters Trust Principles.