It initially opposed a merger, but agreed to explore one under pressure from creditors and unions.

It initially opposed a merger, but agreed to explore one under pressure from its unsecured creditors' committee and unions.

S1, which had so far opposed a merger with ACI, said its board recommended that its stockholders tender shares into the exchange offer.

In a separate letter, Subaru Motor Co said it opposed a merger "as we believe it would limit the competitive balance" among North America's railroads.

In a survey published Dec. 7, Cowen & Co found 71 percent of shippers opposed a merger of Canadian Pacific and Norfolk Southern.