Three top bond fund manager says that a weakening U.S. economy will lead the Federal Reserve to enact “QE3” — another round of quantitative easing — and they are positioning their portfolios accordingly.

“I just don’t think that we have a healthy fundamental foundation for the economy and therefore surprises are likely to be on the negative side,” Jeffrey Gundlach tells Bloomberg, which reports that his fund, which invests in mortgages, had 34% of its money in non-agency residential mortgage-backed securities as of March 31.

Bill Gross, meanwhile, says the economy will need more QE, though recent comments from Fed officials damped the possibility that it will occur. He told Bloomberg in late March that the Fed would probably shift focus to buying mortgage securities to keep borrowing rates low when its “Operation Twist” program ends in June. And, in an April 4 post on Twitter, he said, “Without QE, the financial markets and then the economy will falter.” Gross increased holdings of mortgages last month to the most in almost three years, Bloomberg reports.

Fellow top bond fund manager Dan Fuss said this week that the Fed may stick with quantitative easing until after the presidential election or the unemployment rate falls to about 6% from its current 8.2%, Bloomberg adds.