The head of the extremist Islamic State group has said it will fight to the last man.
The comments by the militant group's leader, Abu Bakr al-Baghdadi, came in an audio statement, his first since a U.S.-led alliance began conducting airstrikes targeting the group in Iraq and Syria.
In the statement, released Thursday on social media networks, he says his fighters "will never leave fighting, even if only one soldier remains."
"O soldiers of the Islamic State, continue to harvest the soldiers. Erupt volcanoes of jihad everywhere. Light the Earth with fire," he said. "O Allah, deal with America and its allies. O Allah, harshen your grip on them... Deal them the worst of defeats they will ever suffer. Divide their gatherings, split their body, dismember them completely and make us raid them and not them raid us."
The recording appeared authentic, and his voice appeared to correspond with previous recordings released by the group.
Al-Baghdadi's statement came after rumors that he was wounded in an airstrike. It was not clear whether the recording was made before or after the incident.
It also was unclear why the message was only an audio recording. Al-Baghdadi has made only one public appearance since declaring himself caliph, delivering a sermon at a mosque sermon in June in the Iraqi city of Mosul. An earlier audio recording from him is believed to have inspired militants in Algeria to behead a French national.
The latest recording was his first since the US and other partners in the alliance began an air campaign against the extremist fighters in both Iraq and Syria. Other messages from the group, including videos of US and British captives being beheaded by the group, have shown other speakers.
In Washington, US Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, told Congress on Thursday that the United States would consider dispatching a modest number of American forces to fight with Iraqi troops as they engage in more complex missions in the campaign against Islamic State militants.
"I'm not predicting at this point that I would recommend that those forces in Mosul and along the border would need to be accompanied by U.S. forces, but we're certainly considering it," Dempsey told the House Armed Services Committee.
Defense Secretary Chuck Hagel said the coalition had made progress against the militants since beginning its efforts in September.
"ISIL's advance in parts of Iraq has stalled, and in some cases been reversed, by Iraqi, Kurdish, and tribal forces supported by US and coalition airstrikes," Hagel said in testimony to the House Armed Services Committee, using an acronym for the Islamic State group. "But ISIL continues to represent a serious threat to American interests, our allies, and the Middle East ... and wields influence over a broad swath of territory in western and northern Iraq and eastern Syria."
The mostly Sunni extremists have seized large parts of Syria and Iraq. They later announced their proto-state straddling the two countries, where they have implemented a violent interpretation of Islamic law, including public beheadings, massacring rebellious tribes and selling women and children of religious minorities into slavery.
President Barack Obama had authorized the deployment of advisory teams and trainers to bolster struggling Iraqi forces. Obama's plan could boost the total number of American troops in Iraq to 3,100. There are about 1,400 U.S. troops there, out of the 1,600 previously authorized.
Al-Baghdadi said in his statement that the coalition effort had failed to repel his fighters.
"They thought and they estimated, they planned and they conspired, and they prepared to hit the Islamic State, and then they emerged with a failed plan that was to shell the sites of the Islamic State, and its brigades and its vehicles and its soldiers to halt its advance ... but quickly the failure of this plan was apparent," he said. "Soon the Jews and Crusaders will be forced to descend to earth, and to send its ground forces to its end and destruction, by God's will."
He pointed to the announcement of additional troops as proof the airstrikes were not working.
"And here is Obama, sending another 1,500 troops, claiming they are advisors, because the strikes of the Crusaders that continue night and day on the sites of the Islamic State have not halted its advance," al-Baghdadi said.
He urged Muslims to wage holy war everywhere, and to attack and kill "apostates" in Saudi Arabia and Yemen specifically. He also vowed that his group's advance would "reach Rome." Islamic militants often refer to Rome as a symbol of Europe.