European Central Bank officials are back from their summer break and with the hawks pushing for a slowdown in bond buying, Thursday's meeting could prove a key market event.

The ECB's chief economist Philip Lane believes it is too early for the ECB to lay out plans to wind down the €1.85 trillion Pandemic Emergency Purchase Programme (PEPP).

But this week the ECB should set the pace of PEPP buying for the final quarter of the year, a decision that has taken on greater significance given the taper talk.

"The most likely outcome - and smartest thing to do - is still to do nothing," said Pictet Wealth Management strategist Frederik Ducrozet.

Here are five key themes on the market's radar.

Will the ECB change the pace of its PEPP bond buys?

The ECB has kept PEPP bond purchases at a "significantly higher" pace since March to support a Covid-hit euro zone economy.

While some adjustment is possible, Professor Philip Lane has argued it would be at the margins so the ECB can maintain "favourable financing conditions".

Professor Philip Lane, the ECB's chief economist

Piet Haines Christiansen, chief strategist at Danske Bank, reckons the ECB will cut bond-buying to January-February levels of €60 billions a month from the current pace of €80 billion.

Removing a reference to "significantly higher" would be "an elegant way" for the ECB to communicate the slowdown, he said.

Still, the ECB is likely to stress that it has the flexibility to ramp up buying if needed and that any slowdown is not a taper.

When will the ECB start discussing life after PEPP?

With the economy rebounding, policymakers such as Austria's Robert Holzmann say now is the time to discuss how to end the PEPP, which runs until March.

ECB doves will likely push back. Philip Lane argues that markets will not need much notice as the ECB will continue buying bonds via another scheme to meet its 2% inflation goal.

Many economists reckon December is the most likely timing for the post-PEPP debate.

"It's too early to talk about this taper when the Delta variant is still a concern," said Eric Vanraes, a portfolio manager at Eric Sturdza Investments.

Waiting until Decemeber and after the November US Federal Reserve meeting would make the most sense, he said.

What are headwinds to the long-term growth outlook?

The ECB publishes its latest forecasts on Thursday and Vice President Luis de Guindos has flagged upward revisions to growth estimates.

The economy has held up well despite the spread of the Delta variant, thanks in part to the European Union hitting its target of fully vaccinating 70% of its adult population.

But the ECB may be pressed on what the uncertainty posed by other Covid-19 variants means for the outlook, as well as signs global growth is peaking.

If inflation is at 10-year high, are price pressures still transitory?

Euro area inflation rose to 3% in August, challenging the ECB's view that rising price pressures are driven by one-off temporary factors.

Expect the ECB and chief Christine Lagarde to stick with this view and stress that inflation will likely languish below target in coming years.

But supply bottlenecks linked to the pandemic have lasted longer than anticipated and business surveys suggest costs for factories are rising. Then again, wage pressures - a key focus for the ECB - remain subdued.

What would a disorderly market reaction to a Fed taper mean for the ECB?

Expectations for the Fed to slim its bond buying have risen since the ECB last met, while Norway and New Zealand are preparing to hike interest rates.

The ECB will likely be among the last to exit pandemic-era stimulus, but policymakers will be watching how markets react to any Fed taper.

After all, officials were alarmed early this year when expectations for a strong US recovery sparked a jump in Treasury yields that pulled euro zone borrowing costs higher.