(CNN) The leader of the Islamic State of Iraq and Syria, Abu Bakr al-Baghdadi, seems to have broken his 11-month silence with a long audio message in which he mocks the United States, calls on jihadis to rally against the Syrian regime and insists that ISIS 'remains' despite its rapid loss of territory.
A spokesman for the US Office of the Director of National Intelligence, Timothy Barrett, told CNN that after analyzing the recording, the intelligence community has determined the message "appears to be authentic."
The speech seems to have been recorded relatively recently, as it references North Korean nuclear threats against Japan and the United States, as well as Syrian peace talks -- in which Russia, Turkey and Iran are trying to extend ceasefires across Syria.
The release appears to lay to rest claims by the Russian military that they had almost certainly killed Baghdadi in an airstrike near Raqqa on May 28. US officials say ISIS has largely been forced out of Raqqa as well as Mosul, and Baghdadi may be somewhere in the middle Euphrates River Valley.
That is an area that straddles Syria's border with Iraq, to which much of the group's leadership is thought to have relocated earlier this year.
A spokesman for the US-led coalition fighting ISIS said they were not aware of the audio recording. "This is the first I've heard about it," US Army Col. Ryan Dillon, a spokesman for Operation Inherent Resolve, told reporters Thursday at the Pentagon by teleconference from Baghdad.
Dillon later added "without verifiable evidence of his death we have continued to assume he's alive." Dillon said he was "sure our people" are looking at the recording, and if there is any information in the recording as to his location "we may have folks moving in right now."
In his 46-minute message, Baghdadi urged fighters ("the mujahideen") to persevere, and to show that the bloodshed in Mosul, Raqqa and elsewhere was not in vain "by clashing the shining swords and shedding filthy blood."
He appealed for jihadi attacks worldwide, claiming that "America, Europe and Russia are living in a state of terror," according to a translation provided by the SITE Intelligence Group, which tracks jihadi groups. Baghdadi also rallied Sunni Muslims against the Shia, saying that they would never accept "half-solutions" -- especially after all the destruction and the gains they've made. This appears to be a reference to Iran's growing reach across the region.
Scholar Hassan Hassan, who has written a book about the rise of ISIS, said in a tweet that a key theme of Baghdadi's speech was that he sees ISIS's fight as a "ceaseless war of attrition to deplete enemies." In that regard, Baghdadi claims the US decision not to send ground troops to Syria as vindication of ISIS's strategy. (In fact, the United States has several hundred combat troops in Syria.)
Baghdadi says the US suffers from fatigue and Russia has taken control of the Syria situation. Baghdadi also echoes the message of another ISIS leader, Abu Mohammad al-Adnani, who declared that holding territory mattered less than the will to fight. Adnani was killed in 2016.
In his speech, Baghdadi says that the prophet had not told his companions when or how Islam would be victorious, "so that they don't make victory or defeat dependent upon losing territory or some of the believers being killed."
Both US and Russian air power, as well as a variety of ground forces, are active in the area, but ISIS still holds some towns on the Euphrates.