SAO PAULO, March 14 (Reuters) - Brazilian shopping mall operator Aliansce Sonae has increased its offer for a tie-up with rival BR Malls by 10.9%, it said on Monday, after having a previous proposal rejected by the latter.

The company said in a securities filing it has decided to bump a cash payment offer by 500 million reais ($98.53 million) to 1.85 billion reais and give 51.08% of the combined company to BR Malls shareholders, from 50% previously.

Aliansce will submit the new offer to a BR Malls shareholders' meeting, it added, given it already holds a 5.05% stake in it.

The firm said that it is "convinced that the business combination is a unique opportunity to strengthen both companies, with significant gains for their shareholders, customers, and other stakeholders."

"Aliansce Sonae and its financial advisors have been interacting with BR Malls' shareholders, which, for the most part, have shown support for the consummation of the intended transaction."

The company had first submitted an offer in January for what it called a merger of equals between the firms, but that was unanimously rejected by BR Malls board.

Since Aliansce's first offer, BR Malls also revealed talks with homebuilder Gafisa SA and fellow mall operator Ancar Ivanhoe over possible combinations of assets.

BR Malls has a market capitalization of 7.5 billion reais, while Aliansce Sonae has a market capitalization of 5.54 billion reais, Refinitiv Eikon data showed.

Aliansce is backed by the Canada Pension Plan Investment Board (CPPIB) fund and also has Alexander Otto's ECE and founder and chairman Renato Rique as major shareholders. BR Malls, on the other hand, has a more diffuse ownership. ($1 = 5.0745 reais) (Reporting by Gabriel Araujo, Editing by Louise Heavens)