Sen. John McCain (R-Ariz.) on Tuesday called on President Barack Obama to attack the Islamic State’s stronghold in Syria, after a video was released showing the apparent execution of American photojournalism James Foley by the group known as ISIS or ISIL.

“The more he (Obama) delays and the more he acts incrementally, the more ISIS adjusts and the more difficult they will become,” McCain said, according to the Arizona Republic. “And one of the decisions that he has to make is to attack ISIS in Syria because they are moving the captured equipment there and they are fighting there and their enclaves are there.”

Sen. John McCain, R-Ariz., said Tuesday that the Obama administration needs to fight the Islamic State in Syria. (AP Photo/Ross D. Franklin)

“They have erased the border between Iraq and Syria. They are now an enclave larger than Indiana,” he added.

McCain called the video of Foley’s execution “just horrible,” and said it shows Obama was wrong to downplay the rise of ISIS.

“This is the most vicious terrorist organization that we’ve ever encountered,” McCain said. “This president has ignored the threat for a long period of time, and now we’re paying the price.”

He added he hopes the video “gives us more of a wake-up call.”

Sen. Marco Rubio (R-Fla.) responded to the video Wednesday morning by saying ISIS has “declared war on the United States,” and that Obama needs to realize this fact.

“I remain deeply concerned that despite the preponderance of evidence that proves ISIL is a fundamentally evil and dangerous terrorist threat to the United States, President Obama continues to appear unwilling to do what is necessary to confront ISIL and communicate clearly to the American people about the threat ISIL poses to our country and to our way of life,” Rubio said.

“ISIL is not a problem for only Iraqis or Syrians to solve,” he added. “A piecemeal approach will not eliminate the growing threat to the United States and our allies.”

White House officials said last year that they believe they have the authority to launch new airstrikes in Syria without approval from Congress, based on the idea of defending U.S. national interests. White House Counsel Kathryn Ruemmler made that comment when the administration was considering action to counter the use of chemical weapons in Syria.

Obama considered strikes against Syria, but backed away from that threat. Later, Syria agreed to a deal with Russia to hand over its chemical weapons.

While the Obama administration has stepped up its campaign of airstrikes against ISIS targets in Iraq, Obama has stressed repeatedly that he does not support the introduction of substantial ground force in Iraq.

Obama was scheduled to speak about the Foley video early Wednesday afternoon from Edgartown, Mass.