(CNN) -

Republicans in Congress have begun their most forceful push yet in urging President Barack Obama to begin a military campaign into Syria to defeat the Islamic State in Iraq and Syria.

"One of the key decisions the President is going to have to make is air power in Syria. We cannot give (ISIS) a base of operations," Sen. John McCain, R-Arizona, said on "Fox News Sunday."

For nearly three years, Obama has refused to engage in a complicated civil war in Syria where different factions are fighting each other and attempting to topple President Bashar al-Assad.

The President has actively defended his decision to not get involved in the war-torn country. But now that ISIS, which gained prominence and power in Syria, is expanding its scope, the domestic calls for the President to act in Syria are loud.

Conservatives pushing for military action dominated the Sunday political talk shows less than one week after an ISIS militant with a British accent beheaded American journalist James Foley in a video of his killing.

"I don't want to hear from the President about how he's reacting to events," U.S. Rep. Paul Ryan, R-Wisconsin, said on CBS News' "Face the Nation." "I want to hear a strategy how he's going to fend ISIS off."

Sen. Lindsey Graham, R-South Carolina, said on CNN's "State of the Union" that it is to "America's peril" if ISIS is not stopped.

"It's about time now to assume the worst about these guys, rather than to be underestimating them," he said on CNN's "State of the Union."

Defense Secretary Chuck Hagel gave a stark assessment of ISIS on Thursday, indicating the terror group, which has expanded its grip to western Iraq, needs to be addressed.

"This is beyond anything that we've seen. So we must prepare for everything. And the only way you do that is you take a cold, steely, hard look at it and get ready," Hagel said.

At the same news conference, Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said the U.S. is going to expand its reach to address ISIS. He refused, however, to confirm that the U.S. would conduct airstrikes in Syria.

"It requires a variety of instruments, only one small part of which is airstrikes. I'm not predicting those will occur in Syria, at least not by the United States of America. But it requires the application of all of the tools of national power -- diplomatic, economic, information, military," he told reporters Thursday.

Graham said the United States must do everything it can to defeat ISIS, even if that means U.S. ground troops become engaged.

"If our military commanders tell us that we need ground forces to defeat ISIL, which is a threat to the United States, so be it," he said.

But Sen. Jack Reed of Rhode Island, the only Democrat to appear on the Sunday shows to talk about ISIS, pushed back against the idea that U.S. troops should enter into another ground war.

"The most effective use of our force is not putting troops on the ground, but using capable troops like Kurds with (U.S.) airstrikes," Reed said.

Threat to the United States

The Republican lawmakers said their calls for expanded military action are justified because ISIS poses an "imminent threat" to the United States.

"We should, in my view, look at ISIL as a direct threat to the United States," Graham said, using the alternate name for ISIS.

Graham's assessment mirrors all of the other top Republicans who appeared on political talk shows Sunday, who insisted that ISIS is capable of committing an attack on U.S. soil.

"I do think they present the greatest threat we've seen since 9/11," Rep. Michael McCaul, R-Texas, said on ABC's "This Week."

Top military officials issued dire warnings about the severity of ISIS and their mission without saying ISIS posed an immediate, direct threat to the United States.

Dempsey described their mission as "apocalyptic," and Hagel called the threat "imminent ... to every interest we have."

McCaul, the chairman of the House Homeland Security Committee, said he believes an attack on the U.S. is in the works.

"They would love more than nothing else to hit the United States of America," he added.

Rep. Mike Rogers, Michigan Republican and chairman of the House Intelligence Committee, said the estimated 100 ISIS fighters who are American citizens and "thousands" that hold European passports make it easy for the trained militants to enter into the United States.

"They are one plane ticket away from U.S. shores," Rogers said on NBC's "Meet the Press."

Reed, a top Democratic member on the Senate Armed Services Committee, however, softened the immediacy of the threat.

"But to jump from what they have done, which is horrific, particularly the murder of Mr. Foley, to the assumption that they're going to be an immediate and within days a threat to us here in our homeland, I think you don't jump to that assumption, but you don't dismiss it," he said on "State of the Union."

But Graham fired back: "Here is the question. Can America be safe if ISIL is not defeated? I don't think we can."

Criticism of Obama

Republicans blamed the President for the expansion of ISIS, saying the terror groups' dominance stems from a lack of inaction in Syria when that country's civil war broke out nearly three years ago.

"I am heartbroken ... about what has happened to the Syrian people and a lot of that is due to our total inaction. And it's going to be one of the more shameful chapters in American history," McCain said.

Sen. Kelly Ayotte of New Hampshire said the President's limited foreign policy is no longer acceptable.

"The containment aspect of it is not going to defeat them," Ayotte said on CBS News' "Face the Nation."

McCaul echoed that same sentiment: "I don't think you're going to win this with a containment policy alone. This administration thus far has only dealt with containment."

"This is an opportunity for the President to take a step back, change his presidential guidance," Rogers said.

Congress' role

Members of Congress have not yet expressed concern that the Obama administration has acted unilaterally by launching nearly 100 airstrikes in northern Iraq.

More concerning to Republicans are cuts to the defense budget that cost more than half a trillion dollars, or 10% of its budget, over 10 years as part of an effort to reduce overall government spending.