Federal Reserve Chair Jerome Powell told Congress on Tuesday he does not expect federal legislation will be needed to address the expiration of a major benchmark interest rate that underpins trillions of dollars worth of financial contracts worldwide.

The rate in question is the London Interbank Offered Rate (LIBOR), which is set to expire in 2021.

“If we need a federal law change, we will let you know,” Powell told the House Committee on Financial Services when asked about LIBOR. When pressed, he added, “I don’t think we think we need a federal law change.” Powell said the Fed is committed to preparing banks to switch over to another benchmark—although he did not specify which one—by the end of next year.

U.S. Rep. Brad Sherman (D-Calif.) urged Powell (roughly the 46-minute mark) to provide Congress with a more definitive answer.

“I hope you can act within a month to let us know,” Sherman said. Businesses “need to legally know about what to switch over to. We want to avoid the multi-billion-dollar lawsuits when somebody says it should be this, instead of that.”

Established by the Financial Conduct Authority in the United Kingdom based on submissions from numerous large banks, LIBOR is a daily rate in multiple terms referencing multiple currencies that establishes an average interest rate used by banks as they borrow from one another. After discoveries of manipulation, U.K. authorities ultimately determined they would no longer require banks to provide the reporting necessary to support LIBOR after 2021, suggesting its veracity as a benchmark rate would disappear.

Sherman joked that the mere mention of life after LIBOR in a Congressional setting could set financial markets on edge. “We’re impairing the economy because we’re talking about this today,” he said.

But he’s not that far off. LIBOR’s expiration is causing uncertainty with $200 trillion in notional transactions in the cash and derivatives market alone, according to the Fed-formed Alternative Reference Rates Committee (ARRC), whose task was to find a suitable U.S. currency-based replacement for LIBOR. Nearly 20 percent of those contracts extend beyond 2021, ARRC said.

One possible successor to LIBOR is the Secured Overnight Financing Rate (SOFR), a measure of the cost of borrowing cash overnight collateralized by U.S. Treasury securities.

In 2017, ARRC selected SOFR as its preferred alternative to LIBOR, and some major companies—like Fannie May, Barclays Bank and Royal Dutch Shell—have begun pegging future contracts to SOFR.

But SOFR is still not the unanimous choice, even in the United States.

Notably, the Securities and Exchange Commission has refused to endorse any particular successor rate, while simultaneously urging financial institutions to choose a LIBOR alternative and alert shareholders to potential disruptions to their contracts caused by LIBOR’s expiration.

The lack of clarity at the federal level is causing lawmakers in New York state to consider legislation that would “reduce the adverse economic outcomes” on contracts in the Empire State underpinned by LIBOR after 2021.