The US central bank is expected to hike interest rates for the fourth time as US growth continues to look solid.

Investors are concerned, however, about slowing international growth, volatile stock markets and the possibility of a slowing US economy, and will focus on any indications from the Fed that it may be close to pausing its tightening cycle because of these issues.

"The market's thinking more and more the Fed may be just about done, it's not quite there, but it's not got a lot yet to go," said Michael Schumacher, head of rate strategy at Wells Fargo in New York.

Comments from Fed Chairman Jerome Powell in late November that the key interest rate was "just below" neutral, a level that neither brakes nor boosts the economy, increased speculation that the Fed may end rate hikes sooner than previously expected.

They came after similarly dovish comments from Fed Vice Chair Richard Clarida.

Investors on Wednesday will watch for any modification in the Fed's language that shows that it may take a meeting-by-meeting approach to raising rates, as opposed to indicating that it has a predetermined number of rate hikes that are still likely, said Schumacher.

"Is it meeting-to-meeting or not? I think that's what people are really keen to look at," he said.

The Fed has indicated that three additional rate hikes are likely next year, based on the median expectations in its rate projections known as the "dot plot." If this falls to two rate hikes or less, it will signal to markets that the Fed is closer to pausing its rate hikes.

Interest rate futures traders are pricing in less than one full rate hike during 2019, which is down from two full rate hikes at the end of October, according to the CME Group's FedWatch Tool.

Benchmark 10-year notes gained 3/32 in price to yield 2.848 percent, after earlier dropping to 2.821 percent, the lowest since Aug. 27. The yields have fallen from a seven-year high of 3.261 percent on Oct. 9.