Four key World Trade Organization members have reopened trade talks to see if an agreement can be reached ahead of a key deadline.
The US, Brazil, India and the European Union (EU) are meeting for five days in Germany to see if a global trade deal is still possible, the EU said.
Attempts to resolve the Doha round of trade talks have failed to date, after disagreement over farming subsidies.
The talks will not “finish Doha” but see if a deal is possible said the EU.
Agriculture and farming subsidies have been a major sticking point between the US, EU and developing nations in the Doha round of talks - named after the Qatari capital where discussions started in 2001.
Jagdish Bhagwati, an economist at New York’s Council for Foreign Relations said the four members were in the “final game of making concessions, but this should have happened months ago”.
The EU has argued that the US caused the talks - which were meant to boost trade as a means to tackle poverty - to collapse.
Similarly the US has said Europe has failed to open up its markets.
Mr Mandelson is attending the talks along with Mariann Fisher Boel, the agriculture commissioner of the EU.
Also present are US Trade Representative Susan Schwab and Agriculture Secretary Mike Johanns.
Brazilian Foreign Minister Celso Amorim and Indian Trade Minister Kamal Nath are also at the event, which is taking place in Potsdam.
The need to resolve trade talks has intensified as US President George W Bush’s special “fast-track” authority to negotiate trade deals ends this month.
President Bush’s Trade Promotion Authority will expire after 30 June, meaning that the US Congress will again have the right to amend such agreements.