SYDNEY, Dec 13 (Reuters) - Canadian dairy Saputo Inc on Friday said it had extended its offer for Australia's Warrnambool Cheese and Butter Factory Co by a week, pending a regulatory proceeding.

Saputo, Canada's biggest dairy company, is in a three-way battle with Australian rivals Murray Goulburn Co-operative Co Ltd and Bega Cheese Ltd for Warrnambool, which is attractive as a platform for sales into China.

But Saputo's offer was dealt a blow two weeks ago when Australia's Takeovers Panel stopped the company from processing acceptances for its A$515 million offer.

Murray Goulburn, the second biggest holder in Warrnambool, had asked the panel to stop Saputo from processing acceptances and block the Canadian company's most recent offer. The injunction on processing acceptances can last up to two months.

Saputo pushed back the closing date of its offer period by a week to next Friday, the company said in a filing to the stock exchange, buying itself more time.

Saputo said it had received acceptances totalling 15.7 percent of Warrnambool, just below the stakes held by Murray Goulburn and biggest holder Bega Cheese.

Saputo declared its bid unconditional on November 25, and said it would hike its offer if it won control.