About $630 million in Stone Container Corp. debt has been placed on CreditWatch with negative implications because of the proposed purchase of a Canadian firm, Standard & Poor's Corp. said Friday.

Stone earlier this week announced its intention to buy Consolidated-Bathurst for $2.2 billion.S&P said that while its ratings incorporate some debt capacity for acquisitions, "the magnitude of this bid is well beyond Stone's previous acquisition prices and may raise financial risk in the coming years to levels inconsistent with the current ratings."

But S&P said a downgrade of Stone's rating is not inevitable.

"Stone could have robust levels of free cash flow during the next few years to rapidly pay down debt. Also, the deal should enhance and diversify Stone's business risk profile. Consolidated-Bathurst is a well-regarded Canadian forest products concern with a large presence in newsprint."

No deadline was set for determining any changes in rating.