WASHINGTON  President Obama, speaking to an enthusiastic audience of union officials in Lanham, Md., on Tuesday, underscored his embrace of nuclear power as a clean energy source, announcing that the Energy Department had approved financial help for the construction of two nuclear reactors in Georgia.

If the project goes forward, the reactors would be the first begun in the United States since the 1970s.

The announcement of the loan guarantee  $8.3 billion to help the Southern Company and two partners build twin reactors in Burke County  comes as the administration is courting Republican support for its climate and energy policies. With climate legislation stalled in the Senate and its prospects for success dim, Democrats are seeking new incentives to spur clean energy development and create jobs.

At the same time, the president’s embrace of nuclear energy has drawn the ire of environmental groups that have long opposed any return to a reliance on nuclear power.