Investa Listed Funds Management Ltd., Investa Office Fund's responsible entity, gave Blackstone Group LP until Oct. 18, 5 p.m. Sydney time, to match or beat Oxford Properties Group's A$5.60-per-unit takeover offer for the listed Australian fund.

The ultimatum was given to the U.S. private equity giant after the Toronto-based suitor submitted a binding proposal Oct. 12 at the completion of a four-week due diligence process. Investa Listed also deemed Oxford's offer as superior than Blackstone's A$5.52-per-unit bid, which reflects an aggregate A$3.3 billion value.

Investa Listed said that it will finalize discussions with the real estate arm of the Ontario Municipal Employees Retirement System if Blackstone does not present a matching or superior offer, but maintained that its directors continue to unanimously recommend the American firm's rival offer.

On Oct. 10, Oxford Properties became the largest shareholder of Investa Office after the completion of a deal with Investa Commercial Properties Fund for the purchase of a 19.99% shareholding in the targeted real estate investment trust.

Oxford Properties' proposal is still subject to the execution of a scheme implementation agreement and the unanimous recommendation of Investa Listed's directors. In a letter sent to Investa Listed, the Canadian bidder said the takeover is expected to be implemented within 2018 along with the payment of the cash consideration for Investa Office's unit holders.