"October is probably a sweet spot for them to announce tapering, because you then tell market participants early enough and you give the people, who deal with the nitty gritty of the purchase program enough time to prepare for a start in January", Elga Bartsch, chief European economist at Morgan Stanley in London, said before the decision.
The ECB will be closely watched for any signs that the central bank has become uncomfortable with the euro's recent strength, a concern that could delay it from winding back its massive monetary stimulus scheme. Growth forecasts were largely unchanged except for 2017, which was revised up from 1.9% to 2.2%. The euro jumped 0.9 percent to $1.2022.
The prospect of lower inflation would typically weaken the euro.
Even so, while the single currency struggled to hold onto all of its initial gains the GBP EUR exchange rate remained under pressure on Thursday afternoon.
The ECB retained its main interest rate, for main refinancing operations, at zero per cent, while the interest rates on the marginal lending facility and the deposit facility will remain unchanged at 0.25 per cent and negative 0.4 per cent respectively.
Thanos Vamvakidis, a senior foreign exchange strategist at Bank of America Merrill Lynch, agreed the ECB had to comment on the Euro.
Analysts say this is making the decision on when the bank begins to rein in its stimulus more complicated. The ECB also needs to decide how to address the issue of the firming euro.
As a result of this and persistent Brexit concerns, most analysts predict the Pound Euro exchange rate will continue to weaken in the long-term.
Another surprise came from Bank of Canada, as it raised interest rates by another 25 basis points for the second meeting in a row.
The purchases are set to run at 60 billion euros per month through the end of the year, and longer if needed to raise the inflation rate.
The strong euro means the price of imports falls, reducing inflation, and it also makes eurozone goods less competitive globally, threatening to dampen exports and so hit growth. Against the buck, it's up almost 14% this year. According to the ECB President Mario Draghi, the euro inflation is "more muted than one would expect" due to external factors such as the collapse in global oil and commodity prices, the output gap, and the global slack.
The dollar struggled on Monday with a trade-weighted basket approaching a 2-1/2 year low as North Korea's latest nuclear tests prompted a rush to unwind bets with the euro the only notable exception to the broad market sell-off.