Mohamed El-Erian, CEO of Pimco, expects the Federal Reserve to announce its plans for mortgage-backed securities and Treasury tapering this week, with El-Erian predicting the Fed will reduce its acquisitions in the $10 billion-to-$15 billion range initially. 

El-Erian made these predictions in an interview with CNBC:

The Fed's long-awaited two-day September meeting begins Tuesday and it's widely expected that central bank policymakers will announce that it is starting to reduce its $85-billion-a-month asset purchases.

At the conclusion of its meeting on Wednesday, the Fed will provide interest rate guidance and economic projections, and Fed Chairman Ben Bernanke will hold a news conference.

"They're going to try to strengthen the forward guidance in order to minimize the impact on markets of the taper," the Pimco CEO and co-CIO added in a “Squawk Box” interview.