"We never pre-commit." This was the rule broken last week by the European Central Bank's Chief Economist Peter Praet, one of the more dovish members of the bank's Governing Council, as he openly said it would start to discuss the gradual exit from of its quantitative easing (QE) program this week at its meeting in Riga, Latvia. What has changed? Recent headline inflation was stronger than expected and close to the ECB's target, mainly due to the rise in oil prices. At the same time the situation in Italy has calmed down again. But there still are risks to the growth outlook from other issues such as the U.S.-EU trade spat. "We think a 'flexible tapering' announcement is more likely than an unconditional commitment to an end date for QE," said ECB watcher Frederik Ducrozet at Pictet Wealth Management in a note.

"The ECB could say that there will be 'no further large expansion of asset purchases' barring an unwarranted tightening of financial conditions. The modalities of QE tapering could be decided in July." Whether the details come in June or July, the overwhelming majority of economists polled by Reuters expect the purchases to end by the end of this year. "Irrespective of whether the exit announcement is in June or July, we expect QE to end in December after a taper in (the fourth quarter) and the first policy rate hike in June 2019," said Mark Wall, the chief economist with Deutsche Bank, in a research note.