Superior Plus says it's no longer planning to buy Canexus Corp. through a friendly takeover that would have combined two of Canada's largest industrial chemical companies.

Toronto-based Superior Plus (SPB.TO) made the announcement Thursday morning, days after the U.S. Federal Trade Commission said it would try to block the transaction because of its impact on competition in the sodium chlorate market.

Calgary-based Canexus (CUS.TO) and Superior had previously said they were prepared to fight the commission's challenge.

But Superior Plus said Thursday that it's exercising its option to terminate the offer because the two companies haven't been able to work out details that would have allowed them to extend a deadline of Wednesday to finalize the merger.

The companies announced the all-stock agreement on Oct. 6, saying it valued the Canexus equity at $316 million. Including the assumed debt, the deal was worth $932 million at the time of the announcement.

The agreement included a provision for either company to pay a $25 million fee to the other under certain circumstances if the transaction didn't go through, but it wasn't immediately clear if those provisions would be triggered.