Wisconsin Governor Scott Walker is thinking about running for President of the United States, but in one of his biggest national addresses yet, he made a comparison between the Islamic State of Iraq and the Levant (ISIL) and public sector unions, igniting controversy.

On Thursday, the governor spoke to a gathering of ultra-conservatives in Washington, DC, spending most of his remarks attacking US President Barack Obama on a whole host of issues, including foreign policy.

"I want a Commander-in-Chief who will do everything in their power to ensure that the threat from radical Islamic terrorists do not wash up on American soil," the Republican governor told the crowd.

When he was asked later what he would do to fight ISIL, he referred to his experience scanning FBI threat assessment reports while in office.

He then made a reference to his ongoing standoff with public sector unions in his state over pay and benefit cutbacks.

"If I can take on 100,000 protesters, I can do the same across the world," he said.

That did not sit well with the unions, who are calling the comparison nothing short of scandalous.

"To compare hardworking men and women who work for a living to terrorists is a disgrace," said Phil Neuenfeldt, President of the Wisconsin AFL-CIO (The American Federation of Labor and Congress of Industrial Organizations).

"Coming together to peacefully protest for freedom, to raise your voice for a better Wisconsin, this is not an act of terror."

Requests by DC Dispatches to Governor Walker's office for clarification of his comments were not returned.