Economic conditions in the United States have largely returned to normal and a Federal Reserve decision to raise interest rates should come soon, Atlanta Fed President Dennis Lockhart has said.

"I think the point of 'liftoff' is close," Lockhart said in a speech to the Atlanta Press Club. "The economy has made great gains and is approaching an acceptable normal ... conditions are no longer extraordinary."

He later told journalists he was "very disposed" to a rate increase at the Fed's September policy meeting, but emphasised that the path of subsequent hikes should be gradual. 

He defined a gradual path as being more frequent than every other meeting.

His comments, coming on top of similar remarks by other Fed policymakers, signal the US central bank's growing recognition that its full employment target may be close at hand, while progress on lifting inflation to a steady 2% rate remains elusive.

Labour market strength appears to have set the stage for a rate hike next month, but it remains something of an act of faith that inflation will eventually recover as well.

In an interview with Bloomberg TV yesterday, Fed Vice Chairman Stanley Fischer said the US economy had "nearly full employment but very low inflation." Fischer added that rates would not stay this low "forever."

Lockhart is regarded as a centrist and possible swing vote on the Fed policy committee, and his steadily firming language about the US economy has served as a barometer of the central bank's willingness to take that leap.

Lockhart said the US economy had cleared several major hurdles that worried him earlier in the year and was now strong enough to handle the end of more than six years of near-zero rates.

Risks from abroad, whether a Greek exit from the euro zone or a meltdown in China, have receded, he said, while job growth has left the US economy "just a shade" from full employment and put the Fed in reach of one of its key goals.

While oil prices have made it difficult to gauge inflation, Lockhart said he is confident it will rise toward the central bank's target in the coming months as the economy continues to strengthen.

"Compared to earlier in the year, we know a lot more and can shelve some concerns," Lockhart said. "We are getting closer and closer to what feels like a healed state."

Since May, Lockhart has pointed to a likely September rate hike, and his comments have firmed alongside continued strong job growth. 

Four of the current ten voting members of the Fed policy committee have publicly put September in play - Lockhart, Fed Governor Jerome Powell, San Francisco Fed President John Williams and Richmond Fed President Jeffrey Lacker.

Chicago Fed President Charles Evans is the only policy committee member to have taken a public stand against a hike next month, though others like New York Fed President William Dudley and Fed board member Lael Brainard have cited overseas risks and other issues they feel could slow the US recovery.

Fed Chair Janet Yellen has said she feels a rate hike will be appropriate later this year, without indicating a preference.

But Lockhart said he agreed with Yellen and many others that the rate hike path should be gradual once an initial increase is approved, saying a slow rise was needed to nurse the US recovery.

"Policy will likely transition from being aggressively stimulative toward merely stimulative," Lockhart said.