By Balazs Koranyi
FRANKFURT (Reuters) - European Central Bank policymakers are wary of making any new change to their policy message in April after small tweaks this month upset investors and raised the specter of surging borrowing costs for the bloc's indebted periphery, six sources told Reuters.
One of the officials, who are in or close to the Governing Council, even said the ECB had been overinterpreted by markets at its March 9 meeting.
Taken aback when markets started to price in an interest rate hike early next year, policymakers are keen to reassure investors that their easy-money policy is far from ending, suggesting a reluctance to change message before June, the sources said.
The euro, the bloc's government bond yields and banking stocks fell after the Reuters article was first published.
While the current level of bond yields remains acceptable, a further increase would be problematic, particularly in places like Italy, Spain and Portugal, where debt payments are a major cost item and rising yields would curb spending and thwart growth.
With the euro zone economy on its best run in almost a decade and conservative policymakers keen to start winding down stimulus, the ECB gave a small nod to improvement with a tweak of its guidance in early March, axing a reference to being ready to act with all available instruments.
But that message did not come across as hoped.
"We wanted to communicate reduced tail risk but the market took it as a step to the exit," one of the sources said. "The message was way overinterpreted."
Indeed, yields surged and investors quickly priced in a rate hike for the first quarter of 2018, even as policymakers tried in vain to play down those expectations.
The market move was exacerbated when Austrian central bank chief Ewald Nowotny openly discussed another possible change in bank's guidance, hinting at a major debate under the surface -- speculation that the sources dismissed.
ECB Chief Economist Peter Praet has been in damage control mode since, arguing that there is "strong logic" backing up the guidance, which stipulates that asset buys would have to end before any interest rate hike.
The ECB declined to comment.
With inflation below the ECB's target for four straight years until recently, the bank has cut rates deep into negative territory and plans to buy at least 2.3 trillion euros worth of bonds, all in the hope of cutting borrowing costs enough to revive growth and, with it, inflation.
Some have argued that with the economy on more solid footing, the ECB could soon eliminate the punitive interest rate charge, raising the deposit rate to zero, even as asset purchases continue.
"That would be a communication nightmare," one of the sources said. "If you raise rates, you can't communicate that it's a one-off, only back to zero, then we stop again."
"The market would immediately price in a new rate path, pushing the entire curve sharply higher."
With the euro zone government debt at 91.3 percent of GDP, not far below the 94.5 percent peak hit in 2014, governments can hardly afford big rises in borrowing costs that could cap public spending, thwarting investment and growth.
The sources also argued that the market may not be accurately pricing risks related to the new U.S. administration, like the possibility of trade wars, protectionism, financial deregulation or President Donald Trump's difficulty in pushing his agenda through Congress.
Banks, the biggest losers from negative rates, have meanwhile benefited from the steepening of the yield curve this year so there is no urgency to give them a hand, the sources added.
Inflation having hit 2 percent last month, essentially meeting the ECB's target, also put some pressure on policymaker as German criticism of loose monetary policy heated up.
"Inflation has peaked for now and the oil price is down 10 percent so we are far from having to worry about too much inflation," a third source said.
While the sources acknowledged unexpected strength in the underlying economy, they said it was difficult to communicate this through policy statements, especially with underlying inflation showing few signs of moving up.
"A small change in the wording can easily be blown out of proportion," one of the sources said. "There is a communication risk and I would argue for stability."
(Editing by Jeremy Gaunt and Catherine Evans)