SYDNEY (Reuters) - Australian office landlord Investa Office Fund IOF.AX said it will study a $2.4 billion takeover bid from Canada's Oxford Properties Group, an offer that was criticized by rival suitor Blackstone BX.N which also threatened to drop its own bid.

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Oxford had lobbed a last-minute A$3.3 billion ($2.4 billion) offer for Investa on Tuesday that was A$90 million higher than U.S. private equity firm Blackstone Group’s bid which had already won the backing of the target.

Investa said on Wednesday it is adjourning a planned shareholder meeting for Thursday that was set to vote on Blackstone’s offer while it weighs the attractiveness of Oxford’s bid.

Blackstone, in a letter to Investa, said the Oxford offer was “not a superior proposal” and that it reserved its rights to terminate its bid and claim a break fee if the meeting were to be adjourned and Oxford’s offer deemed better.

“The alternative proposal is subject to completion of full due diligence ... (and) there is a lack of funding certainty for the transaction,” the letter, which was released to media, said.

A Sydney-based spokeswoman for Oxford Properties Group, the real estate investment arm of Canadian pension fund OMERS, was not immediately available for comment.

Investa has been a takeover target for years, as tight supply and strong growth lift rents in Australia, especially in Sydney where the company’s towers are concentrated.

Oxford’s offer is also slightly above the book value of the 20-property portfolio, which, besides Sydney, includes towers in Brisbane, Melbourne and Perth.

But, according to Blackstone, its rival lacks experience in Australia and does not have funding secured for the deal.

“It is our belief that pursuing the alternative proposal will provide uncertainty to IOF unitholders,” the letter says.

Investa units closed 2.3 percent higher on Wednesday at A$5.44, below Oxford's A$5.50 per unit offer but above Blackstone's A$5.3485. The broader market .AXJO was 1.0 percent lower.