Police mounted a heavy presence outside the Barcelona hotel where the policymakers started meeting at 0700 GMT, ahead of protests against the Spanish government's spending cuts that are supported by the ECB.

Financial markets want the central bank to step up its efforts to fight the crisis by buying Spanish government bonds to reduce borrowing costs for the country which is in recession and has unemployment that is twice Europe's average.

But ECB policymakers are more likely to praise Spain's cost-cutting drive than to announce any new policy action such as restarting the bond-buy program and it is expected to leave interest rates unchanged at a record low of one percent.

Investors will focus on whether President Mario Draghi leaves the door open to easing policy later this year if the crisis gets worse at his 1230 GMT (8.30 am EDT) news conference.

"I think the reactivation of the SMP (bond-buy program) will occur only at a point at which the situation has deteriorated significantly and I think the pressure would have to be greater than we've seen in recent weeks," said RBS economist Nick Matthews.

Spanish bond yields jumped at a debt auction that was held as the 23-member ECB Council met but demand was solid. The ECB has pumped over 1 trillion euros into the financial system in recent months, smoothing debt issuance for euro zone members.

Draghi helped shift the tone of the economic policy debate in the euro zone last week when he advocated a "growth compact" without spelling out exactly what he meant.

French presidential candidate Francois Hollande, who wants to step away from German-inspired austerity, has welcomed Draghi's comments and the ECB president will be pressed to flesh out his growth vision.

Draghi has so far pressed governments to shape up their economies with structural reforms but there is growing resistance to spending cuts that governments across the euro zone are making to streamline public finances.

BUNDESBANK PRESSURE

The Italian is under pressure to limit the ECB's role from Bundesbank chief Jens Weidmann, who wants countries to put their finances in order rather than looking to the central bank.

"A consistent budget clean-up and determined structural reforms are the best growth policy, because that way trust is achieved and economic performance is strengthened," Weidmann told German weekly newspaper Die Zeit.

Draghi also faces resistance from the powerful Bundesbank to any potential rate cut or a reactivation of the bond-buy plan.

"The euro crisis has not escalated to such an extent recently that he would want to take on the Bundesbank on that," Berenberg Bank economist Holger Schmieding said of the bond-buy program.

The ECB has left its bond-buy plan dormant for the last seven weeks despite a rise in benchmark Spanish yields to 6 percent. A break above that, to 7 percent, is considered an unsustainable price to pay to refinance its debt.

Weidmann told Reuters last month Spain should take the rise in its bond yields as a spur to tackle the root causes of its debt woes and not look to the ECB for help.

A Reuters poll taken last week showed three-quarters of economists saw the ECB restarting its bond purchases within the next three months. However, most money market traders said in a separate poll the bank would not buy more bonds.

AUSTERITY FATIGUE

Spain and its problems are at the heart of a downturn of confidence in the euro zone, where fatigue with austerity is growing just as the economy shows signs of deteriorating.

The euro zone purchasing managers' index (PMI) showed the euro area's private sector slump deepened in April at a faster pace than any economist polled by Reuters predicted, dampening hopes the region will emerge from recession soon.

The prospect of the euro zone as a whole following Britain into recession has set markets wondering whether the ECB could pave the way for a rate cut later this year. It has never before lowered its main rate below 1 percent.

Draghi said last week any "exit strategy" from the ECB's emergency measures - long-term lending operations and the dormant bond plan - was premature given weak economic conditions and he has not ruled out cutting rates below 1 percent.

"He will probably emphasize the downside risks to growth without getting close to signaling a rate cut for June," said Berenberg's Schmieding.

"A June cut is not likely but it is not impossible and he will likely keep the options open when asked about it."

ECB Vice-President Vitor Constancio said after the publication of the PMI data there were "very significant" risks to the economy, adding the bank would adapt its policy if those risks became a reality, as it did when it cut rates last year.

If that view makes it into the ECB policy statement, rate cut expectations that have begun to creep back into market pricing in recent weeks are likely to firm rapidly.

(Writing by Paul Carrel; Editing by Jeremy Gaunt and Anna Willard)

• A Permanent Economic Emergency