While Federal Reserve policymakers are now in agreement over gradually tapering its bond purchases, as the question of when to further withdraw its easing arises, the gloves will come off, says Alan Blinder, former vice chairman of the Fed.

"Once the Federal Open Market Committee (FOMC) announces a few more $10-billion-a-month taperings of asset purchases, the financial markets will fixate completely on the Federal Reserve's eventual exit from its current extraordinarily easy monetary policy," he writes in The Wall Street Journal.

That may happen around July 30, says Blinder, now a Princeton University economist. "And it will probably be accompanied by a revival — likely a loud revival — of the hawk-dove wars at the central bank."

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The two sides will battle over how quickly to raise interest rates and shrink the Fed's balance sheet, Blinder writes.

The central bank's federal funds rate target now stands at a record low of zero to 0.25 percent, and its balance sheet has bulged to more than $4 trillion.

The economy's strength will determine the timing of the Fed's exit, Blinder says.

While Blinder believes the Fed will shrink its portfolio through a natural roll-off, which means as the securities mature they are not replaced, he doesn't think that will be enough.

"I've always doubted that roll-off would be enough; my guess is that the Fed will have to engage in active selling. Which is hardly the end of the world," he explains.

"The Fed acquired its enormous balance sheet by buying Treasurys, agency debt and mortgage-backed securities in the open market. It will shrink the balance sheet by selling some of those same securities back in the open market. Not exactly rocket science."

Meanwhile, concern has arisen in recent days about signs of a global economic slowdown. Former Pimco CEO Mohamed El-Erian says the Fed and other central banks should refrain from further easing in response.

"This time, we should not look to another round of policy experimentation by hyperactive central banks as sufficient to stabilize markets, promote healthy growth and chop the tail risk of deflation," he writes in the Financial Times.

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