Investa Office Fund has set next Monday as the date for its shareholders to vote on Blackstone Group's sweetened $3.3 billion takeover bid.

Blackstone Group has declared its $5.52 per share offer as final.

The US private equity giant increased its offer for the Sydney-focused landlord last week in response to a rival bid from Canada’s Oxford Properties Group.

Oxford, which already owns 10 per cent of Investa, offered $5.50 per share compared with the US buyout giant’s previous bid of $5.3485 per share.

A Sydney-based spokeswoman for Oxford Properties Group, the real estate investment arm of Canadian pension fund, declined to comment.

Australia’s commercial property sector has defied a softening in home values.

With overall unemployment sitting at a six-year low, economic growth surging and city downtown capacity barely growing, demand is outstripping supply.

The face-off between the North American firms is indicative of a reach for yield by global investors amid strong Australian commercial rents, especially in Sydney, where downtown capacity is tight.