As the Fed launches one lending program after another, investors are now calling for the Federal Reserve to aim its sights on the more than $9 trillion U.S. corporate bond market.

Following the example of the European Central Bank, the Fed could add corporate bonds to the list of assets it is buying to restore normalcy to a bruised corner of financial markets that has seen a freeze-up in liquidity amid worries that even large corporations may default on their obligations, according to Hans Mikkelsen, head of U.S. investment-grade strategy at Bank of America Global Research, in a Tuesday note.

See: European Central Bank announces massive stimulus plan to calm markets

“Corporate credit has become a big concern for investors and, as we have seen in Europe, central banks can sharply improve pricing given illiquidity. Obviously it will take some time for the Fed to set it up but the announcement itself would be very powerful,” he said.

Former leaders of the Federal Reserve Janet Yellen and Ben Bernanke have called for the buying of corporate debt. “To avoid permanent damage from the virus-induced downturn, it is important to ensure that credit is available for otherwise sound borrowers who face a temporary period of low income or revenues,” they wrote in an essay published by the Financial Times (paywall).

Read: Bernanke, Yellen suggest Fed should move to start buying corporate debt

Mikkelsen estimates $4.5 trillion of investment-grade bonds that could be eligible for purchase if the Fed starts buying corporate debt.

The U.S. central bank has already launched a raft of initiatives to prop up lending and support large businesses, which are at risk of seeing their cash flows dwindle and revenues slump due to the COVID-19 outbreak. The Fed launched the commercial paper funding facility on Tuesday, backstopping a source of fund for highly-rated businesses by buying commercial paper from eligible issuers.

See: Federal Reserve launches crisis-era commercial paper funding facility

Snapping up corporate bonds “seems a small step since they just set up a facility to buy commercial paper and, if little else, would be useful to calm a market that is basically broken at this point, with large outflows that look set to continue and pent-up issuance,” said Mikkelsen.

As prices for corporate debt securities take a hit, investors have pulled out billions from mutual funds and exchange-traded funds that follow the corporate bond universe.

The value of the iShares iBoxx USD Investment Grade Corporate Bond ETF LQD, -0.18% has fallen around 16% year-to-date, and the fund has seen more than $4.2 billion of outflows. The S&P 500 SPX, -1.11% has slumped 26% over the same period.

The one-way selling and unwillingness of broker-dealers to buy into the market has also contributed to a lack of liquidity. Investors have complained the hefty cost to buy or sell even highly rated corporate bonds have discouraged trading activity.

Read: Oil market crash exposes liquidity drought in corporate debt trading

Adding to the pain, yields for government paper have also risen this week as investors sell highly liquid securities to raise cash, hurting corporate debt prices that are benchmarked to the prevailing U.S. Treasury yield.

“The problem currently is that investors seemingly sell all they have, which includes Treasuries and thus corporate bond prices face a double whammy of wider spreads and higher interest rates,” said Mikkelsen.