WATCH: Trump talks about his plan for defending the U.S.
Donald Trump warns that anyone who attacks American troops with chemical weapons would get a "big league" response from the United States if he becomes president.
In an exclusive interview with Circa on Thursday, he said the recent ISIS mustard gas attack on U.S. troops at a training facility in northern Iraq would be the equivalent of his red line --a warning given by President Obama to Syrian President Bashar al-Assad that the use of chemical weapons would warrant some kind of immediate U.S. response.
We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus. That would change my equation.
President Obama's remark to reporters on Aug. 20, 2012.
"When you look at they're starting to hit us with gas now on top of everything else, that's a total lack of respect and you cannot let them get away with it," said Trump. "You have to go after them big league."
Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, told the Senate Armed Services Committee on Thursday that Islamic State militants targeted a military base in northern Iraq with what he describes as a "sulfur-mustard blister agent."
No one was injured or killed in the attack.
Yet, the use of chemical weapons raises serious questions, considering how the U.S. has responded in the past to similar attacks.
In 1988, then-Iraqi leader Saddam Hussein launched what's considered the largest chemical attack directed at civilians in history when he used chemical weapons against Kurdish civilians in Halabja, killing more than 5,000 people.
Despite global condemnation, the act didn't trigger a U.S. military response.
Military action was used in 2003 when then-President George W. Bush invaded Iraq on faulty intelligence that Hussein was in possession of weapons of mass destruction.
But, there was no action taken after rebel fighters with the Free Syrian Army and civilians accused al-Assad of using chemical weapons on the civilian population in rebel-held territories or Sarin gas in Ghouta, Syria.
The issue is a difficult one for Clinton, who backed Obama's call for a red line against Syria. On an interview Thursday with MSNBC, Clinton spokesman Robby Mook couldn't explain the last-minute change of policy by the administration to not take action against al-Assad.
Trump says the answer is easy. He said anyone who uses chemical weapons should expect military action.
"You have to hit them so hard and the people that did it," said Trump. "Don't forget they're out there looking to do it again."
You can follow Sara A. Carter on Twitter @SaraCarterDC.