Most longer-dated bond yields were down 2 to 7 basis points on the day <DE30YT=RR> <BE30YT=RR> <IT50YT=RR>, as markets recouped some of the losses incurred during a big sell-off over the last week.
While the ECB is expected to cut interest rates and deliver other stimulus measures on Thursday, reports on differences in opinion on resuming a fresh asset-purchase round have pushed yields higher almost across the board this week.
Germany's 10-year bond yield is some 17 basis points above record lows reached a week ago but it fell 2 bps on Wednesday at -0.572% <DE10YT=RR>, close to one-month highs. Its 30-year yields slipped back below 0% after rising into positive territory on Tuesday for the first time in a month <DE30YT=RR>.
Italian bonds outperformed, with the 30-year <IT30YT=RR> and 50-year <IT50YT=RR> yields both down 7 bps on the day.
Yields had risen on Tuesday on news that the new coalition plans to raise the budget deficit to around 2.3% of economic output next year, risking the reignition of tensions with the European Union.
However, analysts say the appointment of former Premier Paolo Gentiloni as the EU economic affairs commissioner is likely to help smoothen ties.
"There is some re-positioning ahead of the ECB after the sell-off we had over the last few days," said Natixis fixed-income strategist Jean-Christophe Machado.
Whether the ECB disappointed or delighted investors on Thursday, longer-dated bonds would see the biggest impact, Machado added.
The latest leg of the bond sell-off was triggered by a report late Tuesday that the ECB may delay quantitative easing and tie it to upcoming economic data. Many ECB policy-makers favour resuming bond buying but some northern European countries oppose that, Reuters reported last week, citing sources.
"If the ECB doesn't announce QE on Thursday it would be assumed that they will go soon," said Peter McCallum, a rates strategist at Mizuho. "Market expectations for Thursday do seem a bit more realistic."
Curves turn higher: https://fingfx.thomsonreuters.com/gfx/mkt/12/5969/5903/scandi.png
Bond yields have also come under pressure this week from signs the euro zone is moving closer to fiscal stimulus.
The European Union is bracing for a review of its strict fiscal rules as its economy slows, while monetary stimulus is considered close to its limits, according to officials and an EU document seen by Reuters.
Also, a report on Monday said Germany is considering setting up independent public agencies that could take on new debt to invest in the country's flagging economy, without falling foul of strict national spending rules.
Elsewhere, Portugal sold 1 billion euros of 10-year and 15-year bonds at an auction at record low yields.
(Reporting by Dhara Ranasinghe, additional reporting by Yoruk Bahceli; Editing by Mark Potter and Lisa Shumaker)
By Dhara Ranasinghe