All 81 analysts polled by Reuters last week had expected the ECB to keep rates at a 7-year high for the third month in a row, due to its concerns about above target inflation.

But there is growing evidence that the region's economy is suffering after more than a year of financial market turmoil, which has deepened dramatically in recent weeks.

Euro zone unemployment is rising unexpectedly and manufacturing activity is at its weakest since just after the Sept 11, 2001 attacks on the US.

Most analysts expect the problems to pave the way for a rate cut early next year.

Inflation fell to 3.6 per cent year-on-year in Sept, although it remains well above the ECB's 2 per cent threshold.

Trichet will explain the reasons for the decision at a news conference at 8.30 pm. -- REUTERS