General Electric's chief executive will on Thursday unveil to the French government and unions an improved offer for the energy arm of Alstom, a source close to the U.S. conglomerate said of its efforts to fend off a rival proposal.

Alstom's board is due to announce by Monday its choice between GE's 12.4-billion-euro ($16.8 billion) cash offer and a competing proposal by Germany's Siemens and Japan's Mitsubishi Heavy Industries.