The Wall Street Journal is reporting that President Obama wrote his fourth letter to his favorite Iranian pen pal, the supreme leader of Iran, Ayatollah Ali Khamenei, last month, asking the fanatic to join in the fight against Islamic State.

What could go wrong?

The letter appeared aimed both at buttressing the campaign against Islamic State and nudging Iran’s religious leader closer to a nuclear deal.

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 same people say.

The October letter marked at least the fourth time Mr. Obama has written Iran’s most powerful political and religious leader since taking office in 2009 and pledging to engage with Tehran’s Islamist government.

The correspondence underscores that Mr. Obama views Iran as important—whether in a potentially constructive or negative role—to his emerging military and diplomatic campaign to push Islamic State from the territories it has gained over the past six months.

Mr. Obama’s letter also sought to assuage Iran’s concerns about the future of its close ally, President Bashar al-Assad of Syria, according to another person briefed on the letter. It states that the U.S.’s military operations inside Syria aren’t targeted at Mr. Assad or his security forces.

The American government has continuously stated that Assad must go, but we're fighting his enemies in Syria on several fronts.  If you can make sense out of that policy, you win a cookie.

Tying assistance in the fight against the Islamic State to the nuke deal is another bad idea.  The president is already eager to strike an "historic" agreement with the Iranians, and the prospect of Iran helping out the U.S. in the fight against IS in Iraq might lead to even more American concessions.

Mr. Obama’s push for a deal faces renewed resistance after Tuesday’s elections gave Republicans control of the Senate and added power to thwart an agreement and to impose new sanctions on Iran. Sens. Mark Kirk (R., Ill.) and Robert Menendez (D., N.J.) have introduced legislation to intensify sanctions.

“The best way to prevent Iran from getting a nuclear weapon is to quickly pass the bipartisan Menendez-Kirk legislation—not to give the Iranians more time to build a bomb,” Mr. Kirk said Wednesday.

House Speaker John Boehner (R., Ohio) expressed concern when asked about the letter sent by Mr. Obama.

“I don’t trust the Iranians, I don’t think we need to bring them into this,” Mr. Boehner said. Referring to the continuing nuclear talks between Iran and world powers, Mr. Boehner said he “would hope that the negotiations that are under way are serious negotiations, but I have my doubts.”

In a sign of the sensitivity of the Iran diplomacy, the White House didn’t tell its Middle East allies—including Israel, Saudi Arabia and the United Arab Emirates—about Mr. Obama’s October letter to Mr. Khamenei, according to people briefed on the correspondence and representatives of allied countries.

As for Khamenei, he certainly hasn't been very friendly lately.  Here's an excerpt from a recent speech:

“America, Zionism, and especially the veteran expert of spreading divisions—the wicked government of Britain—have sharply increased their efforts of creating divisions between the Sunnis and Shiites,” Mr. Khamenei said in a speech last month, according to a copy of it on his website. “They created al Qaeda and [Islamic State] in order to create divisions and to fight against the Islamic Republic, but today, they have turned on them.”

I'm sure we can expect lots of help from Iran in confronting the Islamic State.