CAIRO, Egypt — The leader of a Qaeda umbrella group in Iraq warned Iran in a new audiotape to stop supporting Shiites in Iraq, giving leaders in the neighboring country two months to sever ties or they would face a “severe war.”

Abu Omar al-Baghdadi, who leads the Islamic State in Iraq, said his Sunni fighters have been preparing for four years to wage a battle against Shiite-dominated Iran.

“We are giving the Persians, and especially the rulers of Iran, a two-month period to end all kinds of support for the Iraqi Shiite government and to stop direct and indirect intervention … Otherwise, a severe war is waiting for you,” he said in the 50-minute audiotape released Sunday. The tape, which could not be independently verified, was posted on a Web site commonly used by insurgent groups.

Iraq’s Shiite-led government is backed by America but closely allied to Iran. The American government accuses Iran of arming and financing Shiite militias in Iraq — charges Tehran denies.

In the recording, Mr. Baghdadi also gave Sunnis and Arab countries doing business in Iran or with Iranians a two-month deadline to cease their ties.

“We advise and warn every Sunni businessman inside Iran or in Arab countries especially in the Gulf not to take partnership with any Shiite Iranian businessman — this is part of the two-month period,” he said.

Mr. Baghdadi said his group was responsible for two suicide truck bomb attacks in May in Iraq’s northern Kurdish region, saying the attacks in Irbil and Makhmur were an example the “Islamic jihad,” or holy war, was progressing in the Kurdish areas.

At least 14 people were killed when a suicide truck bomb struck a government building in Irbil, Kurdistan’s capital, on May 9. Four days later in Makhmur, another suicide truck bomb tore through the offices of a Kurdish political party, killing 50 people. In the recording, the Islamic State of Iraq leader did not mention Saturday’s deadly truck bomb in Armili, a Shiite town north of Baghdad, that killed more than 100 people. The attack was among the deadliest this year in Iraq and reinforced suspicions that Al Qaeda extremists were moving north to less protected regions beyond the U.S. security crackdown in Baghdad.

But Mr. Baghdadi criticized Kurdish leaders for their alliance with Shiites in Iraq’s government and accused them of encouraging unsavory morals.

“The leaders of apostasy … have impeded the march of Islam in Muslim Kurdistan and helped communism and secularism to spread. … They insulted the religious scholars … encouraged vices and women without veils,” he said in the recording.