Levy, chairman and chief executive of EDF, wrote to staff on Friday saying, although the financial context was "challenging", the project had the support of both the French and UK governments.
He said negotiations with the French government to secure the company's financial position were continuing and insisted EDF would not be involved until his conditions were met.
The plans for the power station in Somerset have been plagued by delays and uncertainty over funding.
EDF's chief financial officer Thomas Piquemal resigned over his concerns that the decision on investment at Hinkley Point C was being made too soon, potentially threatening EDF's financial position.
But Andrea Leadsom, a minister in the Department of Energy and Climate Change, insisted his resignation would have "no impact" on the timing of EDF's final decision on investment for the £18bn project in Somerset.
In the letter Levy said: "I am sure that this project is a good project for the group and that, in the near future, all the conditions will come together for it to be definitely launched."
Discussing the need for a commitment from the French government he said: "We are currently negotiating with the French state to obtain commitments allowing us to secure our financial position.
"It is clear that I will not engage EDF in this project before these conditions are met.
"We have already gained agreement that the full dividend for 2015 is to be paid to the state in shares and not in cash, which represents 1.8 billion euro of additional capital for EDF.
"These discussions are ongoing and I am defending our group for the present and especially the future.”
He added: "Contractual and commercial aspects have been thoroughly examined, including by independent experts, and allow us to be confident to definitively launch the project."
French economy minister Emmanuel Macron said on 7 March that the French government had complete confidence in Levy.
He said: "As the French president said on the occasion of the Franco British Summit on 3 March we also reiterate our full support for the Hinkley Point C project."