Oren Dorell, and David Jackson

USA TODAY

President Obama secretly wrote a letter last month to Iran's supreme leader Ali Khamenei that sought to link cooperation in the fight against the Islamic State in Iraq and Syria to a nuclear deal, The Wall Street Journal reported Thursday.

"Mr. Obama stressed to Mr. Khamenei that any cooperation on Islamic State was largely contingent on Iran reaching a comprehensive agreement with global powers on the future of Tehran's nuclear program by a Nov. 24 diplomatic deadline," the Journal reported, citing anonymous U.S. officials briefed on the letter.

White House spokesman Josh Earnest declined to comment on the report Thursday, saying he wasn't in a position to discuss "private correspondence" between the president and other world leaders.

Discussions about the campaign against the Islamic State have taken place "on the sidelines" of the Iran nuclear talks, Earnest said without being more specific.

The U.S.-led air campaign against Islamic State fighters began in August. Iranian-backed Shiite militias and the Iranian Revolutionary Guard Corps began fighting the group on the ground earlier this year. The United States is trying to round up a coalition of nations in an effort to roll back the militants from positions in Iraq and Syria.

White House and State Department officials have stressed, however, U.S. forces are not coordinating with Iran in the fight against the militants.

"The United States will not cooperate militarily with Iran in that effort," Earnest said. "We won't share intelligence with them. But their interests in the outcome (against the Islamic State) is something that's been widely commented upon and something that on a couple of occasions has been discussed on the sidelines of other conversations."

State Department spokeswoman Jen Psaki told reporters Thursday that U.S. policymakers understand Iran has "concerns" about the Islamic State, but "we don't look at it as a linked arrangement."

"We have concerns about (Iran's) military engagement (in Iraq), but I'll leave it at that," she said.

State Department officials confirmed discussions about the Islamic State in Iraq with Iran's Foreign Minister, Javad Zarif, during nuclear negotiations in Vienna earlier this year and at the United Nations headquarters in New York in September.

U.S. diplomats also passed messages to Tehran through Iraqi government officials and through people close to Iraq's Grand Ayatollah Ali al-Sistani, a powerful Shiite religious leader, the Journal reported.

Among the messages conveyed to Tehran was that U.S. military operations in Iraq and Syria aren't aimed at weakening Tehran or its allies, the newspaper reported.

Senator Mark Kirk, R-Ill., who co-sponsored legislation to increase sanctions on Iran if it does not agree to a deal, told USA TODAY in a statement that "America's strongest move to stop a nuclear Iran isn't sending secret presidential love letters to Supreme Leader Ali Khamenei, it's passing the Menendez-Kirk legislation to get a real nuclear deal with Iran."

The White House successfully lobbied Senate Democrats to oppose the bill, saying it would derail negotiations. The bill's prospects for passage will improve in January, after Republicans take control of the Senate.

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