Exchange traded funds (ETFs) that invest in Treasury bonds were lower Wednesday morning as investors marked time before the Federal Reserve interest rate decision and press conference with Chairman Ben Bernanke.

Separately, bond giant PIMCO fired another salvo at U.S. debt, comparing the Fed’s purchase of bonds to a Ponzi scheme.

The Fed’s quantitative easing program has “in essence picked the pockets of Treasury bond investors throughout the world,” PIMCO portfolio manager Tony Crescenzi wrote in commentary on the asset manager’s website.

There are “literally millions of investors worldwide who worry about the alarmingly large U.S. budget deficit and the impact that the U.S. debt dilemma could have on their Treasury holdings,” Crescenzi said. “Investors are no doubt worried they may have bought into an unsustainable scheme: the creation of a scourge of debt so large that the Fed itself has had to purchase the debt to keep the game going.”

The iShares Barclays 20+ Year Treasury Bond Fund (NYSEArca: TLT) slipped 0.5% on Wednesday morning as investors awaited the Fed.

PIMCO bond guru Bill Gross is reportedly shorting U.S. government debt in Total Return Fund.

iShares Barclays 20+ Year Treasury Bond Fund