A Suncor Energy executive says the company won't extend its hostile takeover offer for Canadian Oil Sands past its Dec. 4 deadline.

Steve Reynish, Suncor's executive vice-president of strategy and corporate development, testified today before the Alberta Securities Commission that the company would not extend its offer past the 60-day deadline it set out when it made the offer.

The commission is hearing arguments into whether Canadian Oil Sands should be allowed to keep its defence against hostile takeovers, which establishes that a bid must be open for 120 days.

Suncor Energy took a $4.3-billion all-stock offer directly to shareholders on Oct. 5 after attempts at inking a friendly deal were rebuffed by COS leadership in the spring.

Argues poison pill should be struck down

In response, COS enacted a new shareholder rights plan — also known as a poison pill defence — designed to buy it more time to find alternatives to Suncor's offer.

Suncor argues the shareholder rights plan should be struck down and that COS shareholders should have the opportunity to decide for themselves whether to take the deal.

An affidavit filed to the securities commission says several other parties have been scoping out a deal with COS.

RBC Capital Markets' Jamie Anderson, who is advising COS, said in the filing that 25 parties are kicking the tires and four "highly credible" ones have signed confidentiality agreements.

"I firmly believe that with more time to run our process, there is a good prospect for one or more counterparties to make a proposal," Anderson said in the affidavit.

"In my opinion, a 60-day period to canvass the range of parties interested in the COS opportunity, to permit them to undergo due diligence and to negotiate an alternative transaction is simply insufficient in these circumstances. I firmly believe 120 days is a more realistic time period."

COS has derided the Suncor offer as too low, opportunistic and exploitive.

Canadian Oil Sands says offer too low

"If Suncor had confidence in the merits of its bid, it wouldn't be trying to ram it through by challenging our shareholder rights plan. It would not need to try to steal time for a decision from our shareholders," CEO Ryan Kubik said earlier this month.

Suncor has warned COS shareholders that failing to accept its offer is a risky proposition, given the likelihood of a prolonged downturn in oil prices. Suncor has described its offer as "full and fair" and has signalled it won't be sweetening the deal.

In its filings with the Alberta regulator, Suncor called the creation of a new shareholder rights plan in the face of the offer was "an improper defensive tactic" that the regulator should not allow to remain.

"No Canadian company has ever taken such a step in the face of an offer that complied with the permitted bid provisions of its existing, shareholder-approved, rights plan," Suncor said.

"In essence, the COS Board has taken upon itself the ability to change the very rules it created and its shareholders approved, once the contest had already begun."

Both companies are partners in the Syncrude oilsands project north of Fort McMurray, Alta. COS has a 37 per cent stake, which is its main asset. Suncor has a 12 per cent share of Syncrude and has vast oilsands operations in northeastern Alberta.