• The ECB put forward an emergency bond-buying program in March of 2020 to deal with the economic shock from the pandemic.
• This program, knows as the PEPP, is currently set to last until March 2022 and total up to 1.85 trillion euros ($2.2 trillion).
• Hawkish members of the euro zone's central bank are less keen to use the full amount provided by the emergency purchase program, wary of a long and significant intervention in markets.

Robert Holzmann, the governor of Austria's central bank, told CNBC Thursday that he believed the European Central Bank might be able to start reducing its bond purchases during the summer.

"When we decided in December an extension of the PEPP program we made a change by changing from a volume that needs to be spent, to a volume which can be spent," he said.

"So what amount of money that will be spent is dependent on the quarter in advance and the decision for the third quarter, we'll make (it) at the end of the second quarter, and hopefully, by that time, there will be a possibility to reduce again the purchases," Holzmann told CNBC's "Street Signs Europe."

The ECB put forward an emergency bond-buying program in March of 2020 to deal with the economic shock from the pandemic. This program, knows as the PEPP, is currently set to last until March 2022 and total up to 1.85 trillion euros ($2.2 trillion).

Hawkish members of the euro zone's central bank are less keen to use the full amount provided by the emergency purchase program, wary of a long and significant intervention in markets. But dovish members of the ECB are more cautious about lifting the stimulus pedal too soon given that the euro zone economy is still to fragile.

Reducing asset purchases in the latter half of this year, and fading out the PEPP, could therefore be helpful in this wider debate over the ECB's methods.

The German constitutional court has questioned the legality of the ECB's original asset purchase program, one that was introduced before the pandemic to deal with the 2011 sovereign debt crisis. More recently, the court also stopped the approval of EU-wide fiscal funds, due to concerns that European laws do not allow the 27 EU member states to package up and issue new debt jointly.

Some experts are worried that the court will soon question the ECB's pandemic purchase program as well, which could be an issue for the economic recovery in the region. In the meantime, one of the current risks for the euro zone is a potential increase in borrowing costs as inflation expectations rise.

Earlier on Thursday, ECB member Klaas Knot told CNBC that the central bank could frontload bond purchases as a way to contain borrowing costs (the sovereign debt yields) for euro area governments.

"If it (rising bond yields) is due to better growth and inflation prospects then that's entirely benign, but if it is due to spillovers coming from different regions in the world then I think it is entirely legitimate for us to temporarily frontload some of the purchases," Knot said.

His comment highlights the flexibility of the ECB's purchase program — an element that President Christine Lagarde often refers to.

Upside risks

Overall, the assessment for the euro area seems more positive than a few months back.

In addition to expecting fewer bond purchases in the latter part of 2021, Austria's central bank chief also sees upside risks for the euro zone economy, given that business activity and vaccination rates are picking up.

"There might have been some glitches in vaccination in recent weeks and months," he said, but "with vaccination we have now an instrument which could clearly lead us out of this economic downturn."

The ECB has forecast a 4% GDP (gross domestic product) growth rate for the euro area this year, after the region contracted almost 7% in 2020. The central bank sees GDP standing 2.3% above pre-crisis levels by the end of 2023.