WASHINGTON (CBS News/CBSDC/AP) — Iranian Supreme leader Ayatollah Ali Khamenei announced Monday that Iran has privately refused U.S. requests for cooperation against the Islamic State of Iraq and Syria.

“I rejected U.S. offer to Iran (about) ISIS because U.S. has corrupted its hands in this issue,” Khamenei posted on Twitter, adding that Iranian Foreign Minister Mohammad Javad Zarif rejected Secretary of State John Kerry’s offer too.

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“Our disagreement on Iran’s cooperation with U.S. over ISIS is because the U.S. itself has been involved in creating and spreading terrorism,” he continued.

The Iranian leader claims that America’s goal in planning a war against ISIS is to turn Iraq and Syria into Pakistan “where it can commit crimes whenever it wants.”

Shortly following the Khamenei’s statement, State Department spokesperson Jen Psaki said that the U.S. did have discussions with Iran about combatting ISIS.

“It’s no secret that we have had discussions (with) Iran about the counter-ISIL efforts in Iraq on margins of our P5+1 talks on nuclear issue,” Psaki tweeted.

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Psaki added that the U.S. will not coordinate militarily with Iran.

“ISIL presents a serious threat to Iran as it does to every other state in the region,” she said.

Iran’s rejection comes as diplomats from around the world meet at an international conference in Paris to seek a global strategy to deal with ISIS. Neither Iran nor Syria was invited to the conference.

Kerry has been pressuring allies to show a united front, especially from majority-Muslim nations, saying nearly 40 countries agreed to contribute to a worldwide fight to defeat the militants before they gain more territory in Iraq and Syria.

The White House said Sunday it would find allies willing to send combat forces — something the United States has ruled out — but that it was too early to identify them. The U.S. has so far been alone in carrying out airstrikes.

Several Arab countries offered to conduct airstrikes against ISIS, according to a State Department official traveling with Kerry who briefed reporters on condition of anonymity to discuss diplomat developments during his trip.

A second official gave some examples of what the U.S. would consider a military contribution: providing arms, any kind of training activity and airstrikes.

Muslim-majority countries are considered vital to any operation, although there have only been vague offers of help previously. Iran was struck off the invitation list, and Western officials have made clear they consider Syria’s government part of the problem.

“Ultimately, this is a fight within Islam, within Sunni Islam,” White House chief of staff Denis McDonough told Fox News on Sunday.

“That’s why we know that ultimately to defeat and ultimately destroy ISIL, something that is not only in our interest but in the interest of the countries in the region, they are going to need to take the fight to it,” he said, using an alternate acronym for the group.

“We’ll build, we’ll lead, we’ll undergird, and we’ll strengthen that coalition. But ultimately, they’re going to help us beat them on the ground,” McDonough said.

The reluctance of the U.S. and its major Sunni allies in the region to engage the two nations most eager to combat ISIS is one of the bigger underlying problems, explains CBS News foreign affairs analyst Pamela Falk.

“The only nations which have been out front to offer boots on the ground are Iran and Syria,” said Falk, “and the U.S. doesn’t want it.”

Speaking Sunday on “Face the Nation,” Kerry insisted the objective was not to secure guarantees of boots on the ground — from any nation.

“There are some who have offered to do so, but we are not looking for that, at this moment anyway,” Kerry said.

But securing military commitments of other kinds — to train and equip “moderate” Syrian rebels, carry out airstrikes, and provide intelligence — will be most critical as the Obama administration maintains its promise to keep American combat forces out of the fight.

White House Chief of staff Denis McDonough said Sunday on “Face the Nation” that it will be up to regional partners and Syrian fighters to confront ISIS at ground level.

“We’re going to provide our unique capabilities and airstrikes and intelligence and training and then it will be up to the Syrians on that side of the border to finish the job,” said McDonough.

One of those allies could be Jordan, according to Republican Representative Michael McCaul, who said on “Face the Nation” he had “met with the Prince of Jordan just two days ago, who said he is ready today to put his troops into Syria to fight ISIS.”

But the Paris conference, officially dedicated to peace and stability in Iraq, avoids mention of Syria, the power base of the militant organization gaining territory in both countries by the week. And the U.S. opposed France’s attempt to invite Iran, which shares an 870-mile border with Iraq. The gathering itself will be brief, a matter of a few hours between its start and a planned joint statement.

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