Republicans are sounding the warning that the next 9/11-like terror plot could emerge from the regions of Iraq and Syria that are currently dominated by an extremist group bearing down on Baghdad.

As the Islamic State of Iraq and Syria (ISIS) - which has already captured the cities of Tikrit and Mosul and is threatening to take the capital city as well - grows in strength and numbers, will it pose an immediate threat to the United States homeland as well?

Experts say the group's increasing power and reach is concerning, though it's not entirely clear when they might be able to threaten the U.S.

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"You've got motivation mixed with opportunity, ideology and foreign fighters and all of that looks like a very extreme version of Afghanistan in the '90s, plus what was happening in Iraq after the Iraq war," said CBS News National Security Analyst Juan Zarate. "This is a cauldron of future terrorist threats to the west."

The bigger danger, Zarate said, is that the U.S. does not yet know exactly what the group will look like once it evolves. While ISIS might not launch an attack on U.S. soil tomorrow, he said, "I think the grave threat here is that you have the seeds of a new terrorist movement emerging very aggressively."

Sen. Lindsey Graham, R-S.C., said on CBS' "Face the Nation" Sunday that U.S. officials have warned the next major attack on U.S. soil could emanate from the region.

"The seeds of 9/11s are being planted all over Iraq and Syria," Graham said. "They want an Islamic caliphate that runs through Syria and Iraq...and they plan to drive us out of the Mideast by attacking us here at home."

Graham's concerns were echoed on ABC's "This Week" by Ret. Gen. Peter Chiarelli, who said that "all Americans should be concerned" by ISIS' quick rise and success in Iraq. And on "Fox News Sunday," House Intelligence Committee Chairman Mike Rogers, R-Mich., said, "I guarantee you: this is a problem that we will have to face and we're either going to face it in New York City or we're going to face it here."

"These are not monkey bar terrorists out in the desert somewhere planning some very low-level attack. These are sophisticated, command and controlled, seasoned combat veterans who understand the value of terrorism operations external to the region, meaning Europe and the United States. That is about as dangerous a recipe as you can put together," he said.

There have been some indications this might be the group's intent. Army Col. Kenneth King, who was the commanding officer of a U.S. detention camp in Iraq, told the Daily Beast recently that when current ISIS head Abu Bakr al-Baghdadi was released in 2009, he said, "I'll see you guys in New York."

But Michael Morell, the former acting CIA director and a CBS News analyst on intelligence, national security and counterterrorism issues, predicted it's at least a year before ISIS might pose more of a serious threat to the U.S. The current major threats to the homeland still come from al Qaeda groups in Pakistan and Yemen, he said.

But, Morell added, if it looks like the U.S. influence in Iraq is increasing once again, the threat from ISIS could also rise.

"That's one of the downsides of U.S. involvement," he told CBS News. "The more we visibly get involved in helping the [Iraqi Prime Minister Nouri al-Maliki] government fight these guys, the more we become a target."

President Obama said Friday that he has asked his national security team to "prepare a range of other options" for U.S. involvement, though he is not considering putting U.S. troops back on the ground there.

For now, Morell said that ISIS is principally targeting the Iraqi government. Over the weekend, the group posted graphic photos that appeared to show its fighters brutally killing scores of captured Iraqi soldiers. But Zarate warned about the influence of senior al Qaeda figures who traveled to Syria and could be working to turn ISIS' attention toward the west.

"You do have very senior al Qaeda figures who have migrated to the Syrian conflict to provide strategic guidance and direction and to me that's incredibly dangerous because you have operatives and strategists who have had squarely in mind to turn the attention of these groups toward the west," he said.

One of Rogers' principal concerns is the threat posed by American and European fighters who traveled to what he called "jihadist Disneyland" in eastern Syria and have been radicalized. Just last month, a U.S. citizen linked to al Qaeda terrorists carried out a suicide bombing in Syria.

ISIS "is an al Qaeda-inspired group that certainly has al Qaeda ties, that now has the capability to tap people with Western passports to send them back to Europe and the United States for terrorist activity. That's a problem for us," Rogers said.

In February, Department of Homeland Security Secretary Jeh Johnson said the U.S. was "very focused" on the problem of fighters from the U.S., Canada and Europe who traveled to Syria.

FBI Director James Comey estimated in early May that the number of foreign fighters traveling to the region has grown by a few dozen since the start of the year. Several months before, he had said there were dozens of Americans trying to travel to Syria.

Morell said such fighters are a "growing concern" to the U.S., but that they pose more of a threat as one-man operations at present than a large 9/11 style attack.

ISIS has also been a separate entity from al Qaeda after it was cut off from the main group in February.

The question that remains is whether the U.S. would be able to thwart an attack if one materialized.

Zarate said the country is better prepared to deal with the threat of a terror attack, having built up its counterterrorism capabilities since 9/11. But, he added, "we are, in some ways, blind to a lot of the threats that may be emerging and unable to impact the momentum that some of these extremist groups have."

As the groups grow in strength, "we in some ways then have to play defense, which is a lot harder to do if we're not playing offense at the same time," he said.