The contract, for a minimum of US$4.8 million, paid to Forbes' manufacturing joint venture Phyto-Source LP, was originally signed in September 2002.
It was renewed in June 2004 and under the latest extension is effective until the end of 2006.
"The extension of this agreement is an important event for Forbes as it demonstrates the continued demand for our phytosterol ingredients from an established customer," said Charles Butt, president and chief executive of Forbes Medi-Tech.
Forbes recently expanded the capacity for its cholesterol-lowering ingredient to 1500 metric tonnes, anticipating increased demand for the product in Europe especially.
For competitive reasons, the identity of the customer and contractual terms and conditions could not be disclosed, said Forbes.