Fiat Industrial, the truck and construction equipment maker, has hit a likely delay in plans for a full combination with U.S. unit CNH Global NV after independent directors questioned the terms, sources familiar with the matter said.

The Italian company, spun off from automaker Fiat in 2011, is seeking a merger with its 88% owned tractor subsidiary to compete more effectively with Caterpillar and other peers in both scale and investor appeal.

It had aimed to win approval from the U.S. farm equipment maker's board on October 30 and complete the merger this year.

That timetable now looks unlikely and may even run into 2013 after independent CNH directors raised doubts about the share swap terms for the all-paper offer, two people with knowledge of the discussions said. They asked not to be identified because the talks are confidential.

The merger is "running into problems because the independent board members are having doubts about the share swap ratios," one of the sources said. "It looks unlikely that everything will be ready by the end of the year."