Lockhart said the final decision on a December rate hike remains subject to how the U.S. economy performs over the next few weeks and whether any new perceived risks arise - as happened in August when global market turbulence prompted the U.S. central bank to delay an expected hike in September.
But he said he now thinks the case for what will be the first rate hike in about a decade will only strengthen before the Fed's December meeting.
"At this juncture, it's my assessment that the U.S. economy is likely in an above-potential growth phase, with labor markets continuing to improve, and with an underlying inflationary trend that, if not rapidly moving toward the (Federal Open Market Committee's) objective, is at least not moving away from that objective," Lockhart said. "I think the case for liftoff will continue to firm up."
The pace of rate hikes after that, he said, "will most appropriately be very gradual."
The Fed's specific reference to its "next meeting" in the October statement had a quick impact on investor expectations, which shifted away from betting a rate hike would not happen until the spring. Fed officials had been frustrated by the gap between what markets felt the central bank would do and what most Fed policymakers were saying in public.
With the economy continuing to grow, Lockhart said he felt slack in labor market was "substantially, but not completely, closed."
Federal Chair Janet Yellen said Wednesday that December would be a "live possibility" for a rate hike if the upcoming data are supportive.
"Now no decision has been made on that and, what it will depend on, is the [FOMC's] assessment at the time. That assessment will be informed by all of the data that we collect between now and then," she said, testifying before the House Financial Services Committee.
Yellen also said she and the committee expect the economy to grow "at a pace that's sufficient to generate further improvement in the labor market, and to return inflation to our 2 percent target."
—CNBC's Fred Imbert and Everett Rosenfeld contributed to this report.