Baghdad, Iraq ? A speaker claiming to be Saddam Hussein called on Iraqis in a taped message Friday to rally behind anti-U.S. resistance and promised “days of hardship” for the Americans. He also mocked Washington’s justification for war: “Where are these weapons of mass destruction?”

The broadcast on the Arab television station Al-Jazeera coincided with an escalation in fighting, with an ambush that left 11 Iraqi attackers dead, a mortar attack on a base that wounded 18 U.S. troops and a sniper attack that killed an American in Baghdad.

At the White House, spokesman Ari Fleischer said the CIA would assess the tape, and a U.S. intelligence official said the agency could not verify whether it was truly the ousted Iraqi leader speaking.

The speaker said he was in Iraq and gave the date as June 14.

Reporters and others who have frequently heard Saddam speak said the voice sounded like the former president. The voice contained characteristics similar to Saddam’s style of speech, particularly his typically slow and drawn-out pronunciation. He also maintained his usual defiant, yet calm, demeanor.

If authenticated, the tape — which Al-Jazeera said was delivered to the satellite network by telephone Friday — would be the first solid evidence that Saddam survived the U.S.-led invasion.

Either way, the sudden emergence of a purported message from Saddam threatened to energize anti-U.S. forces and worsen the violence.

“Oh brothers and sisters, I relay to you good news: Jihad (holy war) cells and brigades have been formed,” the speaker on the audiotape said, addressing the Iraqi people.

“There is resistance, and I know you are hearing about this. Not a day passes without them (suffering) losses in our great land thanks to our great mujahideen,” the voice said. “The coming days will, God willing, be days of hardship and trouble for the infidel invaders.”

Saddam loyalists have reportedly been telling Iraqis in villages and markets that he is preparing a comeback and would punish those who cooperate with the U.S. occupation. U.S. officials insist the attacks on Americans are not centrally organized — but say the mystery surrounding Saddam’s fate is serving as a rallying point for anti-U.S. forces.

“I believe the Americans are embarrassed by their failure to catch Saddam,” said Mohammed Abdel-Karim, a university lecturer from Tikrit, Saddam’s hometown. “But they will not catch him. He’s too good in this game,” he added with a smile.

Washington put a $25 million bounty on Saddam on Thursday and offered $15 million for information leading to the capture of either of his sons, Odai and Qusai. The last reported sighting of Saddam was April 9 in the Azamiyah neighborhood of northeastern Baghdad as the capital fell.

Insurgents have been staging ambushes against U.S. forces for weeks, but the latest cycle of attack and counterattack was larger in both magnitude and boldness.

Mortar attacks

Four mortar rounds late Thursday hit a U.S. base near Balad, 55 miles north of Baghdad, wounding 18 soldiers, said Maj. Edward Bryja, of the Army’s 3rd Corps Support Command. Flares and tracer bullets sliced across the night sky after the blasts.

Two soldiers were seriously wounded, with one undergoing surgery in a hospital located on the base and another evacuated for treatment, Bryja said. Others suffered cuts and small punctures from flying shrapnel, and nine soldiers quickly went back to duty, Army officials said.

“This is the first time the base was attacked — and the first time we’ve seen mortars,” Sgt. Grant Calease said. Still, troops at the Balad base were going ahead with a July 4 barbecue.

Random violence

Hours later, 11 Iraqis attacked a U.S. military convoy on a highway near Balad.

Soldiers of the Army’s 4th Infantry Division fired back, killing all the men, the military said. None of the Americans was injured.

Balad is part of an area north and west of Baghdad known as the Sunni triangle — a region where Saddam drew support for his Sunni Muslim-dominated government.

On Friday, attackers detonated an explosive on a highway in Baghdad’s western outskirts, wounding three passengers in a civilian car and two U.S. soldiers traveling in a Humvee convoy, according to an Associated Press photographer on the scene.

A sniper on Thursday shot and killed a U.S. soldier manning the gunner’s hatch of a Bradley fighting vehicle outside the national museum. The Pentagon identified him as Pfc. Edward J. Herrgott, 20, of Shakopee, Minn.

The insurgency has raised fears of a political and military quagmire just two months after President Bush declared an end to major combat on May 1. At least 27 U.S. troops have been killed in hostile fire since Bush’s statement.

Still a holiday

Despite the attacks, many of the U.S. troops held July 4th celebrations at bases around the country.

Some were invited to join Arnold Schwarzenegger for a screening at Baghdad International Airport of his latest movie, “Terminator 3: Rise of the Machines.”

“I play terminator, but you guys are the true terminators,” he told the soldiers.

In the audiotape aired on Al-Jazeera, the speaker claiming to be Saddam said he was still in Iraq “among my people” along with a small group of his “companions.” He said he had been forced to “sacrifice” the government as U.S. troops moved in.

“We … sacrificed what we had to, except our values, which are based on our deep faith and honor. We did not stab our people or our nation in the back,” he said.

Al-Jazeera’s chief editor Ibrahim Hilal, contacted in Doha, Qatar, said the tape was delivered to the satellite network by telephone on Friday.

“Someone called us and played back the tape for us and we recorded it. It ran for over 20 minutes, but only 10 minutes are newsworthy. We don’t know the source or where the call came from. We have no reason to doubt its authenticity,” he said.

The tape was the first purported to be from Saddam since one received May 5 by a reporter for the Sydney Morning Herald, who received a 14-minute audiotape from two men in Baghdad. In that tape, the voice also claimed to be speaking from Iraq and called on citizens to oust American occupiers.