Spokesman Philip Crowley said the announcement was "another desperate act in his campaign to cling to power."
The comments came a day after Gbagbo ordered his government to take control of the country's cocoa purchases and exports, so far dominated by multinational companies, an official said.
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Ivory Coast accounts for 40 per cent of global cocoa supplies, valued at US$4.5 billion a year at current prices, according to London's Financial Times.
Alassane Ouattara, the internationally recognized as the winner of Ivory Coast's disputed presidential election in November, last month extended a ban on cocoa exports, a cornerstone of the economy, to March 15.
The ban is part of a bid to pressure outgoing president Gbagbo to relinquish power.
