She advocated replacing the EU with a "Europe of projects", a loose cooperative of nations that collaborates on ventures spanning business, security and energy on a case-by-case basis.
If she were happy with the outcome of the negotiations, she would recommend staying inside the bloc, she said.
If she was dissatisfied, which would be most likely, she would urge voters to support France's exit, following Britain's example after its referendum last summer.
Le Pen said her first trip abroad would be to Brussels, headquarters of the EU, where she would inform leaders of EU member states of France's intentions.
The European Commission, the bloc's executive arm, would not be welcome at that meeting, she added.
Asked what she would say to German Chancellor Angela Merkel at their first meeting, Le Pen said: "France will now stand up for the interests of France."
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