A U.S. offer to slash its maximum farm subsidies is insufficient for a world trade deal to be reached, French Agriculture Minister Michel Barnier said in an interview published on Monday.

France has repeatedly called on the United States and developing countries to make more concessions in order to salvage the Doha round of world trade talks, calling for more 'reciprocity' from other parties.

"The European Union has no more concessions to make -- it has made many. If we are one reform ahead, the Americans are one behind. I do not think that the new agricultural law in the United States can make up for that," Barnier told the French newspaper La Tribune.

Talks between the United States, the European Union, India and Brazil to try to shape a formula to rescue the troubled round collapsed in June over the size of tariff and subsidy cuts that were required, particularly in farming.

World Trade Organization Director-General Pascal Lamy has said the drive for a global trade pact is now at a "make or break" stage, and negotiators are aiming for the kernel of a deal by the end of the year.

The mood at the talks has brightened recently after reports that Washington could be willing to discuss capping its subsidies at a level as low as $13 billion, provided other countries also make concessions.

Diplomats said the shift in the U.S. position on agriculture could spur advances in other contentious areas of the talks, including industrial goods.

Barnier, however, remained skeptical.

"I do not sense the reciprocity that we expect not only from the Americans but also from the large developing countries," Barnier said.

The farm talks have adjourned while countries work together in small groups and delegates consult with their governments. They resume for two weeks next week, when the industry negotiations move on to substantive issues.