Carrefour and Tesco both started doing it five years ago. Now Asda is getting in on the act too. With the full might of parent company Wal-Mart behind it, Asda has entered into negotiations with big brands to thrash out global supply deals with the likes of Kellogg's, Procter & Gamble and Unilever.

The move is likely to secure Asda better deals for a variety of household brands and, in turn, could lower retail prices - solidifying the supermarket's position as the cheapest of the big four.

"I don't think we've really leveraged Wal-Mart's scale before," Andy Clarke, Asda retail director, admitted last week. But in a world where food inflation is running at 12.5% (according to the latest Grocer 33 data), saving money by securing global deals is more important than ever for retailers.

Asda emphasises negotiations are at early stages, and according to Aidan Bocci, chief executive of consultancy Commercial Advantage, which advises suppliers, it can take years before two parties sign on the dotted line. However, the benefits can be enormous, he says, and suppliers should be optimistic about what such a deal could provide.

"It is all about being really clear about what the supplier can get out of negotiations," he says. "When retailers say 'we want a new set of terms globally', what tends to happen is the supplier either flatly refuses, which sours the relationship, or the supplier caves in.

"But we advise that the starting point should never be 'no'. Suppliers should see a retailer's opening demand for better prices as the chance to reopen negotiations on all manner of areas, such as the amount of senior management time a supplier gets."

Suppliers can also push for greater supply-chain efficiency and penetration in developing countries, he says.

Tesco and Carrefour have been setting up global deals with suppliers for around five years now. "The point is to deliver better value for customers," says a Tesco spokesman. "It is a competitive market, but nobody actually loses because these deals enable suppliers to invest in technology and efficiency through higher volumes. Their costs go down, our costs go down and the consumers pay less.

"We source batteries from a single supplier in China across all the ranges and across the group. That's a lot of batteries. It is hugely to the benefit of the supplier, and it is to our benefit and ultimately it is to the benefit of the customer."

Global deals have enabled Tesco to cut retail prices by between 10% and 15%, according to a source close to the Cheshunt-based multiple. Undoubtedly Asda will be looking to do the same.

While negotiating this kind of deal with brands may be new to Asda, it has benefited from Wal-Mart's strength in accessing better terms on certain own-label and non-food items in the past.

Asda describes the move to deals on big brands as "a natural progression". A spokesman confirmed that it had been working with Wal-Mart to get "the best deals on non-food and private label since 1999". But global negotiations like these can take time to complete.

"It is quite hard for the retailer to make it work," says Bocci. "Effectively they are drawing up an agreement centrally while business is managed at a local level, with lots of negotiations taking place internally. It is not like selling shampoo to one buyer in one category - there are vast numbers of people involved."

If Asda does manage to secure deals with brands, consumers should not expect dramatic differences at the checkout. Asda says any cuts in price are currently "purely hypothetical", and Bocci says the difference will probably amount to only a few pence - "nothing like the variations we are seeing on raw materials," he adds.

For global retailers these deals are becoming increasingly desirable. But there is no precedent for business on this scale and retailers are feeling their way through, according to Bocci. "It is evolving over time, but eventually global agreements will be incorporated in joint business plans.

"There will be rocky patches when agreements swing too far in favour of the retailers, or the suppliers back off because they can't see how to make it work. The destination is the right one, but the road is going to be bumpy."

"There will doubtless be more of the same," agrees the Tesco spokesman. " Wal-Mart is in an unrivalled position to be able to offer global-sourcing deals, so we need to ensure our customers are getting a deal that is at least as good, if not better."going global

How far do the deals stretch?

Tesco has 3,262 stores wordwide and operates in:

UK, US, Ireland, Czech Republic, Poland, Slovakia, Hungary, Turkey, China, Japan, South Korea, Malaysia, Thailand

Wal-Mart has 7,262 stores worldwide and operates in:

UK, US, Mexico, Brazil, Argentina, Puerto Rico, Canada, China, Guatemala, El Salvador, Costa Rica, Nicaragua, Japan, Honduras

Carrefour has 12,217 stores worldwide and operates in:

Argentina, Brazil, Colombia, Dominican Republic, China, Indonesia, Japan, Jordan, Kuwait, Malaysia, Oman, Qatar, Saudi, Arabia, Singapore, Taiwan, Thailand, United Arab Emirates, Algeria, Egypt, Tunisia, Belgium, Cyprus, France, Greece, Italy, Poland, Portugal, Romania, Spain, Turkey