Trade ministers from the US, European Union (EU), India and Brazil are due to meet in London on Monday to try to break a deadlock in global trade talks.
Mr Mandelson faces opposing pressures
The aim is to get a new free trade deal in place by the start of next year, but the US and EU are failing to agree on cuts to farm subsidies and tariffs.
While both agree cuts are needed to aid producers in the developing world, the US says the EU is not going far enough.
Yet France has warned EU trade boss Peter Mandelson to limit reductions.
The French government, wishing to look after its country's large agricultural community, has said it may block any deal if Mr Mandelson makes too many concessions.
Mr Mandelson faces a delicate balancing act to achieve a deal that is acceptable to all sides.
But maintained that he was negotiating in accord with the EU mandate, whatever the French might say.
"The French government doesn't have a veto over the offers the Commission makes and the negotiating tactics I employ," he told the BBC.
At the end of last month, Mr Mandelson offered to cut tariffs on imported food goods by up to 60%, but the US said he was not going far enough, while Paris questioned whether he was exceeding his mandate.
The aim of Monday's talks, which continue in Geneva on Tuesday, is to have a trade deal framework in place ahead of a key World Trade Organization conference in Hong Kong in December.
Mr Portman has already warned that talks could fail
The Hong Kong meeting is timetabled to rubber stamp the final deal, officially ending the Doha round of trade talks which first started back in 2001.
US Trade Representative Rob Portman warned last week that Hong Kong could be a failure unless a breakthrough was made this week.
The dispute over farming is holding up the wider agreement, which will also include new global deals on service industries and industrial goods.
And Mr Mandelson said that more attention should be paid to that wider deal.
He told BBC Radio 4's Today programme:
"The problem is that the round has been pushed, up until now, into an agricultural siding by very aggressive agricultural exporters - the US, Brazil, Australia, countries like this - who, in my view, have interests that don't coincide with the interests of a vast number of developing countries for whom this round is supposed to be operating."