Honda Motor Co. and Nissan Motor Co. called into question an agreement reached less than two months ago to consider combining, casting doubt on their efforts to form one one of the world’s largest automakers.

Shares in Nissan fell while Honda stock closed higher, reflecting investor views that Nissan was more likely to benefit.

Shares of Nissan Motor Co. and Honda Motor Co. rose overnight following reports that the automakers’ proposed merger may be scrapped.