The Iraqi government provided a planeload of ammunition to Peshmerga fighters from Iraq's semi autonomous Kurdish region on Friday, August 8, a U.S. official said, in an unprecedented act of military cooperation between Kurdish and Iraqi forces brought on by an acute militant threat.

The official said Iraqi security forces flew a C-130 cargo plane loaded with mostly small-arms ammunition to Arbil, the capital of Iraqi Kurdistan, in a move that American officials hope will help the region's Peshmerga fighters keep militants from the Islamic State, an al Qaeda offshoot, at bay.

"This is unprecedented," the official said on condition of anonymity.

"Developments over the last few days have refocused the issue, and we’ve seen unprecedented cooperation between Baghdad and Arbil in terms of going after (the Islamic State), not only in terms of conversation but in terms of actual support."

In the first airstrikes in Iraq since U.S. forces withdrew in 2011, U.S. warplanes bombed Islamic State fighters several times on Friday, in an increasingly urgent attempt to halt the militants who have seized a wide swathe of territory since they swept into northern Iraq in June. The hard-line fighters now appear set on trying to take the Kurdish capital.

The grave threat to Arbil, seat of the regional government and a hub for foreign firms in Iraq, appears to have at least temporarily eased a long-running feud between leaders of the Kurdistan region, who have long dreamed of an independent state, and the government of Iraqi Prime Minister Nuri al-Maliki, a Shi'ite Arab who has sparred with Kurds over land and oil.

As Islamic State fighters made another dramatic advance earlier this week, Maliki ordered his air force for the first time to back Kurdish forces in their fight against militants.

The delivery of ammunition on Friday is sure to be welcome for Kurdish officials who for weeks have complained the Peshmerga, whose name means "those who face death," were overstretched and under equipped against the Islamist fighters, who have weapons seized from Iraqi army bases.

Both steps are significant in a country where in recent years Peshmerga and Iraqi forces under the command of Baghdad have been much closer to fighting each another than to cooperating.