ATLANTA — America’s first new nuclear plants in more than a decade are costing billions more to build and sometimes taking longer to deliver than planned.

Licensing delays, soaring construction expenses and installation glitches have driven up the costs of three plants in Georgia, Tennessee and South Carolina, according to an Associated Press analysis of public records and regulatory filings.

Those problems, along with jangled nerves from last year’s meltdown in Japan and the lure of cheap natural gas, could discourage utilities from sinking cash into new reactors, experts said. The building slowdown would be another blow to a drive over the past decade to build 30 reactors. Industry watchers now say that only a handful will be built this decade.

“People are looking at these things very carefully,” said Richard Lester, head of the department of nuclear science at the Massachusetts Institute of Technology.

The review of pending projects found:

Plant Vogtle in Georgia, initially estimated to cost $14 billion, has run into over $800 million in extra charges related to licensing delays. The plant, whose first reactor was supposed to be operational by April 2016, is now delayed seven months.

Tennessee’s Watts Bar power plant, initially budgeted at $2.5 billion, will cost up to $2 billion more, the Tennessee Valley Authority has concluded. The utility said its initial budget underestimated how much work was needed to finish the plant. The project had been targeted to finish in 2012, but has been put off until 2015.

Plant Summer in South Carolina, expected to cost $10.4 billion, has seen costs jump by $670 million; but with lower interest rates and cheaper-than-expected labor, the owners assert the project is still on or under budget.