The United States will have to put boots on the ground if it expects to stop the "horrific killing" at the hands of the Islamic State, Sen. John McCain said Thursday, and that includes stopping Syrian President Bashar Assad.

"In Syria, until we take on Bashar Assad, the other countries such as Jordan and Turkey and the others will not join us," McCain told MSNBC's "Morning Joe" program,  commenting to show host Joe Scarborough that if Assad, "the father of ISIS," is opposed militarily, other Arab countries will add troops to the ground.

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"But right now there is this unholy alliance between the United States and Iran that is delusionary, so we are, therefore, leaving Assad alone, [who] is the client of Iran," said McCain. "It's really one of the most immoral things I've ever seen, especially since we're training young Syrians to go back into Syria to fight Bashar Assad, and we won't protect them from his barrel bombs."

And even though the White House has decided to step up supplies of arms to Syria's rebels, McCain said that will not be enough.

"We are looking at training 500, 1,000 maybe," McCain said of the rebels. "Meanwhile, 20,000 foreigners have flown, moved into Syria and Iraq to join ISIS. The numbers don't add up. There's no way that this idea — it's not a strategy — but this idea can succeed."

McCain said that if the mission is to destroy ISIS, then a strategy needs to be developed that puts American boots on the ground and not to rely on air attacks only.

Meanwhile, President Barack Obama is setting up "straw men" to say people like McCain want to send in masses of troops, which the senator said is not true.

"I'm talking about 10,000 in Iraq," said McCain. "Then we need to say that our objective is to eliminate Bashar Assad as well as ISIS in Syria, and we recruit other Arab nations with Americans, but not too many, to fight against ISIS and Bashar Assad in Syria and coordinate those movements with air power guided by air controls."

But McCain does not think Baghdad would fall to ISIS, even with Iran’s involvement in Iraq, as there are too many people in that city opposed to the group.

"Do we want Iranian-sponsored Shiite militia, who by the way now are committing horrendous war crimes against Sunnis, when we need the Sunni and Anbar Province to join us again — as they did in the past — if we are going to defeat ISIS," said McCain. "The Iranians are on the move, whether it be Yemen, whether it be Lebanon, whether it be Syria, whether it be Iraq, and they are on the move in all of those places. And so they can't be acting in America's interest."

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In another discussion, McCain said he supports Israeli Prime Minister Benjamin Netanyahu's upcoming visit to speak before Congress, as it is "fundamental" that Congress be able to invite any speakers it wishes to.

"But, Joe, I wish all this hadn't happened and I know you do, too," said McCain, calling the way Netanyahu was invited a product of the estrangement between Obama and Netanyahu, and the estrangement between Congress and the president.

McCain said he agrees with Netanyahu that the potential for Iran to acquire a nuclear weapon is an existential threat to Israel, and he understands why Netanyahu wants to address Congress and the American people about it.

Watch the video here.

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