US Trade Representative Rob Portman smoothed over differences with the European Union and instead raised pressure on wealthier developing countries such as Brazil and India.

"In the ideal world you would have on the table some offers on increased access to the emerging developing countries for manufactured products, matched by new proposals on market access to the developed country markets on agriculture," he told reporters at the World Economic Forum in Davos.

"That would be a lot to ask because it involves a lot of risks on the part of all the parties but I think that's what's needed now," he added.

Ministers from about 25 key World Trade Organisation members, including the United States, European Union, India, Brazil, and WTO chief Pascal Lamy were due to hold an informal meeting in Davos on Friday.

Although there have been hopes they would try to move ahead on fundamentals of a trade deal, the Swiss, who organised the meeting, have billed it as an attempt to map out the path for the talks in coming months.

Ministers and senior officials were Thursday already holding private bilateral meetings in Davos in what was widely described as a relaxed atmosphere.

Portman placed the emphasis on opening up industrial and services markets, a key demand industrialised powers like the United States and European Union have been making of their poorer counterparts in return for opening up rich-country agricultural markets.