CANADIAN OIL SANDS LTD 
The Alberta Securities Commission had given Canadian Oil Sands shareholders until Jan. 4 to decide how to respond to the offer.
Suncor on Monday reiterated its all-stock offer of 0.25 of Suncor share for each Canadian Oil Sands share, implying a value of C$8.93 per share based on Suncor's Dec. 31 close.
Suncor, Canada's largest oil producer, is not expected to extend the offer when it lapses on Friday.
"We can only invest so much time and money in this effort and will feel compelled to move on to other opportunities if we don't see substantial support for our bid on Friday," Suncor Chief Executive Steve Williams said.
In a letter to shareholders, Canadian Oil Sands Chairman Don Lowry touted "independence," while calling upon shareholders not to tender their shares.
"Suncor's substantially undervalued bid is set to lapse, and when it does they say they will walk away. For all of us, as shareholders, this scenario reveals a far more compelling and valuable alternative: Independence," Chairman Don Lowry said in a letter to shareholders.
The letter comes as Canadian Oil Sands' shareholder rights plan expires on Monday. The company had adopted the plan, also known as poison pill, two days after Suncor made the offer in early October.
Lowry said the company had also considered a full range of alternatives against the Suncor offer, including a full or partial sale to other parties, and a royalty financing.
"(Canadian Oil Sands) has the financial resources to weather the current downturn," he said, referring to the steep decline in oil prices.
(Reporting by Shubhankar Chakravorty in Bengaluru; Editing by Maju Samuel and Saumyadeb Chakrabarty)
