A senior congressional source told Fox News that there is not anything definitive as to whether the letter even exists. But the source indicated they don’t doubt that it’s true because “we’ve seen [the president] do it before, so there is [a] precedent.”

According to the Journal, Obama has written to Khamenei four times now since taking office.

The congressional source told Fox News that the letter would upset the inroads they’ve tried to make with “the Sunni league,” noting that the president should have informed Congress of this back-channel if it was in fact going on.

“This f***s up everything,” the source said.