Mike Huckabee will be the sole 2016 Republican presidential candidate to address a meeting of the AFL-CIO's executive council later this month, the labor federation said in an announcement. He will be joining most declared Democratic candidates at the private event.

The meeting, which the AFL-CIO has dubbed the "Raising Wages Agenda," will allow top labor leaders to press the candidates on their support of union issues, with trade reportedly being the top concern. The sessions will likely be key to determining who the federation backs in the upcoming election and to what extent.

"The labor movement's doors are open to any candidate who is serious about transforming our economy with high and rising wages. We want to talk to candidates who will deliver and who we can trust to always be on the side of all working people. We want to know who is ready to think and act big enough to seize this historic opportunity," AFL-CIO President Richard Trumka said in the announcement.

Huckabee has long shown an inclination towards economic populism. The former Arkansas governor is the only GOP candidate of any stature to have opposed the recently-passed Trade Promotion Authority legislation, which labor heavily lobbied Democrats to oppose.

In a May statement, Huckabee argued he was not opposed to free trade itself but that President Obama's agenda was nevertheless bad for workers and the economy, criticisms similar to the ones labor leaders made against the legislation.

"We don't create good jobs for Americans by entering into unbalanced trade deals that forgo congressional scrutiny and ignore the law only to import low-wage labor, undercut American workers, and drive wages lower than the Dead Sea," Huckabee said.

Other previously revealed participants at the meeting, which will be held in Silver Spring, Md., on July 29-30, will include Democratic candidates Hillary Clinton, Sen. Bernie Sanders, I-Vt., and former Maryland Gov. Martin O'Malley.