"If there is not a binding accord, there will not be an accord," French President Francois Hollande said in Malta while attending a European Union-Africa summit.
A day earlier US Secretary of State John Kerry made it clear the United States would not sign a deal in which countries were legally obliged to cut greenhouse-gas emissions.
The Paris agreement, he told the Financial Times, was "definitively not going to be a treaty... They're not going to be legally binding reduction targets like Kyoto or something."
Defining the exact legal status of the Paris pact, and which provisions -- if any -- would be legally binding, is one of the toughest issues to be settled in the long-running climate talks.
Also Read
Earlier today, French Foreign Minister Laurent Fabius, also in Malta, described his US counterpart's remarks as "unfortunate".
"We can discuss the legal status of the agreement," said Fabius, who had met Kerry the previous day.
"But it is obvious that a certain number of provisions must have practical effect," he said.
The draft accord being negotiated is divided into a core "agreement", laying out the broad objectives for CO2 reduction and financial aid for developing nations, and "decisions" spelling out how to achieve them.
Negotiations have proceeded from the broad understanding that the "agreement" would have a more binding legal status than the "decisions," which would include voluntary national carbon-curbing pledges subject to revision.
"What we support is in fact a partly legally-binding agreement," a US official, who attended pre-summit ministerial talks in Paris, explained this week.