* OMERS' Oxford ups bid for Investa to A$5.60/share
* Oxford secures support of large Investa investor
* Investa shareholders set to vote on Blackstone (NYSE:BX) bid on Monday
* Oxford calls for meeting to consider Blackstone bid be adjourned
* Blackstone has raised its bid three times
(Recasts with background, Blackstone spokeswoman declines to comment)
By Paulina Duran
SYDNEY, Sept 13 (Reuters) - Canadian landlord Oxford Properties Group has sweetened its bid for Australian office owner Investa Office Fund IOF.AX to A$5.60 ($4.02) per share, escalating a bidding war with private equity giant Blackstone Group BX.N .
The latest salvo from Oxford in the pursuit to buy Investa, which has for years attracted suitors, underlines the Australian firm's value at a time when tight supply is lifting rents in the country, especially in Sydney where the company's towers are concentrated. Blackstone has hiked its bid three times so far.
Oxford's new offer, backed by a top Investa shareholder, is A$0.10 per share higher and values Investa at A$3.35 billion.
It comes just ahead of a meeting scheduled for Monday where Investa shareholders are set to vote on Blackstone's A$3.30 billion, or A$5.52 a share, rival bid. has requested that the Investa "meeting to consider the Blackstone proposal be adjourned" to let the Canadian firm complete due diligence and submit a binding offer, said Paul Brundage, Oxford's head in Europe and Asia Pacific.
Brundage said Oxford had enough money to fund the deal and was prepared to do so with its own funds and third-party financing, and therefore its bid was no longer conditional on completing a financing package as it had earlier indicated.
He made these comments in a letter that was attached to Investa's statement to the Australian exchange on Thursday.
Investa said while its directors continued to unanimously recommend Blackstone's offer, the company was also considering an agreement that Oxford had reached with shareholder ICPF.
The pact allows ICPF to sell up to 19.9 percent of its stake in Investa to the Canadian firm, if Oxford acquires the company.
A Blackstone spokeswoman in Sydney declined to comment.
The firm had previously criticised Oxford, the real estate investment arm of Canadian pension fund OMERS, as lacking experience in Australia, and its offer as highly conditional.
Blackstone made a public A$3.08 billion play for Investa in May. The companies agreed on a deal as the bid was higher than an initial A$5.05 per share approach in April that was kept confidential at the time.
Then Oxford came in with a A$5.50 a share offer earlier this month. Trumping Oxford's first approach last week by 2 cents, Blackstone suggested its A$5.52 bid would be "best and final, in the absence of a superior proposal". Australian takeover rules, bidders must wait four months to re-approach a target after declaring an offer unequivocally final.
Investa shares ended below Oxford's new offer on Thursday. They have risen 11.5 percent since ICPF on Aug. 20 said it had agreed to sell a 9.9 percent stake in Investa to Oxford. ($1 = 1.3916 Australian dollars)