WASHINGTON — Even as the rest of the United States backs away from nuclear power, utilities in Georgia are pressing ahead with plans to build two huge reactors in the next five years — the only nuclear units still under construction nationwide.

On Thursday, Georgia Power asked state regulators to approve its proposal to complete the reactors at the Alvin W. Vogtle generating station near Augusta, home to two existing nuclear units built in the 1980s. The company, which has partnered with three other utilities on the project, said it expected the new reactors would cost roughly $19 billion and come online in 2021 and 2022.

In July, South Carolina utilities abandoned efforts to build two similar reactors, advanced designs known as AP1000s, after delays and cost overruns associated with the project caused local utility bills to soar. That decision left Georgia as the American nuclear industry’s sole hope for an expansion in the near term.

While China is building 20 nuclear reactors, including four AP1000s, the United States has largely abandoned the construction of costly new nuclear plants. Utilities have focused instead on building smaller, less financially risky plants fueled by natural gas, wind or solar power.