The US Federal Reserve's progress in bringing down inflation is "not assured," the chair of the country's central bank said Wednesday ahead of two days of hearings in Washington.

The Fed has hiked its key lending rate to a 23-year high to tackle stubborn inflation, successfully bringing the rate of price increases down from multi-decade highs toward its long-run target of two percent.

But inflation remains elevated, and recent data indicate that the road to two percent could be a bumpy one.

"If the economy evolves broadly as expected, it will likely be appropriate to begin dialing back policy restraint at some point this year," Fed chief Jerome Powell said in a statement.

"But the economic outlook is uncertain, and ongoing progress toward our two percent inflation objective is not assured," he added.

Powell's prepared remarks to lawmakers on the House Financial Services Committee kick off two days of hearings on Capitol Hill, in which he will likely be grilled about when the Fed will start cutting elevated interest rates.

In December, Fed policymakers penciled in three rate cuts this year, but did not indicate the timing of those cuts.

In the months since, policymakers have pushed back against market expectations of an early rate cut, warning against moving too quickly and allowing inflation to reignite.

In his prepared remarks to Congress, Powell said the Fed's rate-setting committee "does not expect that it will be appropriate to reduce the target range until it has gained greater confidence that inflation is moving sustainably toward two  percent."

"We remain committed to bringing inflation back down," he added.

Futures traders have assigned a probability of just over 70 percent that the Federal Reserve will have begun cutting interest rates by mid-June, according to data from CME Group.