Sen. Lindsey Graham (R-S.C.) is slamming former Florida Gov. Jeb Bush, suggesting that his plan to fight the Islamic State in Iraq and Syria (ISIS) is "woefully inadequate."

Without a substantial U.S. presence in Syria and Iraq, it is just a matter of time before ISIL further destabilizes the Middle East and launches an attack against our homeland," said Graham, using an alternative name for the terror group.

There are not enough individuals in Syria that can be effectively trained to successfully destroy ISIL and topple [Syrian President Bashar] Assad."

Graham, who is competing against Bush for the Republican presidential nomination, said that while "it is good that Governor Bush understands we need to do more," his proposal is "woefully inadequate" when it comes to using U.S. ground troops.

With mere incremental changes to the failed Obama policy, the best we could hope for would be the dangerous status quo," the South Carolina Republican added.

Graham released his remarks in a statement after Bush laid out his plan on Tuesday night to combat the terrorist organization. While the former governor said more U.S. troops are likely needed, he added that he doesn't believe a "major commitment of American combat forces" is required.

That's a stark contrast to statements from Graham, who earlier this year said that up to 20,000 troops were needed to fight ISIS.

Graham added on Wednesday that while a no-fly zone in Syria, which Bush endorsed Tuesday, "is a step in the right direction, without troops, the mission is doomed to fail."

It is imperative that regional forces be formed in large numbers. ... For this regional force to be effective and successful, it will require integration of American troops. The American component could range from 5,000 to 10,000 depending on how the force is formed."

Middle East policy, in particular the Iraq War launched by President George W. Bush, has proved at times to be a stumbling block for the GOP contender. And he's taken criticism from the left and right.

In May he told Fox News host Megyn Kelly that “knowing what we know now" he would have authorized the Iraq War.

Bush quickly walked away from his statement, later refusing to answer the "hypothetical" question with another Fox host, Sean Hannity. He eventually said that he would not have invaded, knowing now that the country had no weapons of mass destruction.

But his remarks raised red flags among supporters who worried that it would give Democrats, not to mention other Republican candidates, an opening to connect the former Florida governor to his brother's deeply unpopular war.

Graham, on Wednesday, said that he had "learned from President Bush's mistakes, President Obama's mistakes, and certainly, my own mistakes."

It is disappointing that the president and so many candidates running for the office are unwilling to take these necessary and bold steps before it is too late," he added. "In my view, those reluctant to call for boots on the ground, the only strategy that ensures a stable Middle East and a secure America, are not prepared to be Commander-in-Chief.”

Bush's campaign pushed back against Graham's criticism Wednesday, suggesting the former Florida governor is the only candidate who has offered a "specific, forward-thinking plan." 

Governor Bush is the only candidate in the field who has outlined a specific, forward-looking plan for defeating radical Islamic terrorism," said Allie Brandenburger, a spokesperson for Bush. 

Other candidates, including Hillary Clinton, as confirmed by her campaign, have not put forward any specific prescriptions for addressing the grave threat of ISIS."