The CEO of Suncor Energy is throwing cold water on speculation that its hostile takeover offer for Canadian Oil Sands will be sweetened.

Steve Williams says the $4.3-billion bid is good enough, describing it as full and fair.

Williams says given the gloomy outlook for crude prices and lacklustre performance at the Syncrude oilsands mine, COS shareholders should find the offer compelling.

COS and Suncor are both partners in Syncrude — COS with a 37 per cent interest and Suncor holding 12 per cent.

But Suncor says if it's able to increase its ownership share to just under half, it can do more to help the project run smoothly.

The board and management of COS have rebuffed Suncor's advances, calling the bid exploitative, opportunistic and not in the best interest of shareholders.