* Metro, Tesco sales updates on Tuesday
* Arcandor, Casino updates on Wednesday
* Carrefour, DSG, Home Retail on Thursday
* Ahold, Delhaize on Friday
By Mark Potter
LONDON, Jan 12 (Reuters) - Europe's biggest retailers will show the strain of the economic downturn in a string of trading updates this week, adding to pressure on the European Central Bank (ECB) to deliver a cut in interest rates on Thursday.
Food retailers and discounters will fare better than stores selling discretionary and expensive items, but almost all groups will report a slowdown in sales for recent weeks.
Wal-Mart, the world's biggest retailer, cut its fourth-quarter profit forecast last week as U.S. shoppers curb spending amid rising unemployment and fears of recession.
The picture in Europe is much the same, with business and consumer confidence plunging to record lows in December.
"Given recent largely dismal euro zone data and clearly sharply retreating inflationary pressures, we believe that the ECB is more likely than not to act on Thursday," said IHS Global Insight economist Howard Archer, who thinks the central bank could cut rates by half a percentage point to 2 percent.
Britain's Tesco, the world's third-biggest retailer, is set to buck the trend on Tuesday with a rise of 2.4 percent in underlying sales for the six weeks to Jan. 3, according to a Reuters poll of nine analysts.
That would be an improvement on the 2 percent posted for the 13 weeks to Nov. 22, helped by a seasonal uptick in spending.
But Tesco's Christmas sales are forecast to lag UK rivals due to its greater exposure to non-food lines and to its new discount range, which is depressing top-line growth.
Germany's Metro, the world's fourth-biggest store group, reports 2008 sales on Tuesday.
The food-to-electricals retailer will post revenues of about 68.28 billion euros ($91.44 billion), according to a Reuters poll of nine analysts, up 6.3 percent on last year and meeting its target of over 6 percent.
But that would suggest a slowdown in the fourth quarter, after growth of 7.1 percent in the first nine months, due to flagging sales at Media Markt/Saturn, Europe's top electrical goods retailer, and weaker currencies in eastern Europe.
Several analysts also think Metro will struggle to meet its goal to grow earnings before interest and tax by 6 percent to 8 percent.
German travel and retail group Arcandor publishes a first-quarter sales update on Wednesday.
CA Cheuvreux analysts have pencilled in 0.5 percent sales growth at the group's Karstadt department stores and a 1 percent fall at its Primondo home shopping business.
FRANCE AND BENELUX
After the market close on Wednesday, French supermarket group Casino publishes 2008 sales numbers.
Revenues should reach 28.7 billion euros, according to the average forecast of 18 analysts polled by Reuters Estimates, up 15 percent on the year, boosted by strength at its Franprix and Leader Price discount stores and its South American businesses.
This suggests fourth-quarter sales of about 7.67 billion euros, which analysts think will be held back by sliding underlying non-food sales at hypermarket chain Geant.
A raft of UK retailers publish Christmas sales updates on Thursday, with DSG International, Europe's second-biggest electricals retailer and Home Retail, Britain's top household goods group, both tipped to report big falls in underlying sales.
After the market close Thursday, France's Carrefour, the world's second-biggest retailer, updates on 2008 sales figures.
Following a profit warning in December, analysts expect few surprises, with fourth-quarter sales seen flat or up slightly at 25.3 billion euros to 26 billion euros, according to a poll of seven.
Weakening non-food sales are expected to result in a big fall in underlying French hypermarket sales, offset by a better performance at discount stores and in some emerging markets.
Dutch supermarket group Ahold and Belgium's Delhaize publish 2008 sales numbers on Friday.
Both make over half of their revenues in the United States and so analysts think they will suffer from the same forces that have pressured Wal-Mart, though they note Delhaize's U.S. presence overlaps much more closely with Wal-Mart than Ahold's.
Analysts expect 2008 sales at Ahold to reach 25.73 billion euros, according to Reuters Estimates, suggesting a fourth-quarter sales number of about 6.6 billion euros.
Underlying U.S. sales growth is seen slowing in the fourth quarter, but should be cushioned by the group's drive to lower prices, they said. Underlying sales at Dutch chain Albert Heijn are expected to grow by about 6 percent.
Full-year sales at Delhaize are forecast to reach 18.92 billion euros, according to a Reuters Estimates poll, including a fourth-quarter contribution of about 5.3 billion euros. ($1=.7467 Euro) (Editing by Sharon Lindores)