More than 30 people were killed and more than 60 wounded in a rash of suicide bombings and mortar and rocket attacks in the Sunni Triangle on Saturday, as U.S. Marines and soldiers prepared for a possible assault on the rebel-held city of Fallujah.

The wounded included at least 16 U.S. soldiers injured when a suicide bomber rammed a car into their convoy in Ramadi, 60 miles west of Baghdad, U.S. officials said.

[On Sunday, insurgents launched deadly attacks against police stations in western Anbar province killing at least 22 more people, police and hospital officials said, the Associated Press reported.]

The deadliest violence occurred Saturday morning in Samarra, a city about 65 miles north of Baghdad that U.S. and Iraqi forces retook from insurgents early last month. A series of closely coordinated attacks killed about 30 people, according to tallies by news services, which canvassed hospitals. More than half of the casualties were Iraqi police officers killed in mortar attacks or ground assaults on police stations.

At 9:30 a.m. in Samarra, a car bomb hidden in a stolen Iraqi police truck exploded after U.S. soldiers fired on it as it approached the office of the mayor, who was installed with the backing of U.S. troops last month. One American and four Iraqi soldiers were wounded, the military said.

A half-hour later, a car bomb detonated near a U.S.-Iraqi patrol on the east side of Samarra and a mortar shell hit an outdoor market.

A military spokesman said he could not confirm an Associated Press report quoting a hospital official as saying the fatalities included an Iraqi National Guard commander, Abdel Razeq Shaker Garmali.

"There was an attempt by the insurgents to conduct a coordinated attack, but many of their attempts were ineffective," said Capt. Bill Coppernoll, a spokesman for the 1st Infantry Division. The division issued a statement calling the attacks "desperate" and declaring that its forces, along with at least two battalions of Iraqi forces, remained in firm control of the city of 250,000.

But Samarra residents said the violence threw the city into turmoil. Helicopters roared overhead, gunfire echoed through much of the day and U.S. forces imposed a curfew starting at noon. U.S. and Iraqi forces also closed down the main bridge leading into the city, firing toward boats that attempted to cross the Tigris River.

Hours after the attacks began, Fallujah's mujaheddin shura, or council of holy warriors, which governs the city, issued a statement in which it threatened to "launch wide military operations within the first hours of the U.S. attack on Fallujah, to open several fronts at the same time." The statement said insurgents were standing by in the cities of Baghdad, Kirkuk, Basra and Samarra.

In Baghdad, at least one Iraqi civilian was killed when a roadside bomb exploded near a military convoy in the western part of the city, the military said. Three U.S. soldiers were wounded in the attack.

Explosions echoed across the capital after dark, and residents said they were bracing for insurgent attacks when the U.S. assault on Fallujah begins.

The U.S. military has stepped up operations around Fallujah in advance of an expected offensive to retake the city, which has been controlled by insurgents since April. U.S. warplanes pounded enemy positions and stockpiles of weapons in the city Friday night and into Saturday, while Marine and Army units on the outskirts of the city staged a moonlit battle rehearsal that one Army officer described as a "boxing match" to see what kind of punch the insurgents would throw back.

The U.S. military cordoned off the city and threatened to arrest anyone younger than 45 who tried to flee.

Commanders have said they would not enter Fallujah until Iraq's interim prime minister, Ayad Allawi, gave the word. Allawi, who returned to the country Friday night from a diplomatic trip, was scheduled to give a news conference in Baghdad on Sunday.

"We're here in support of the Iraqi security forces," said 1st Lt. Lyle Gilbert, a spokesman for the 1st Marine Expeditionary Force. "We would make no move without the direction of the interim Iraqi government."

Allawi's government has been negotiating with leaders in Fallujah in an attempt to avert what will likely be an offensive with heavy casualties on both sides. But sources close to the government said Friday that the negotiations had been called off.

[Early Sunday morning, the sound of tanks firing from Fallujah could be heard in a distant but thunderous bass. Helicopters hovered overhead and planes roared across a cloudless sky. The clap of artillery echoed from a Marine outpost near the city in what was shaping up to be another noisy night.]

A delegation from Fallujah headed to Baghdad on Saturday to try to revive negotiations with members of the Iraqi National Assembly, which had requested an effort to end the crisis peacefully. Members of the delegation said the attempt was the last chance before an assault.

"It might be useful that we try. We don't want to blame ourselves when the attack happens," said Maky Nazal, the head of the delegation. "Although the attack is approaching, we have to pay every effort we can to prevent it."

The six-member delegation, four members of the Iraqi Islamic Party and two tribal leaders, were stopped on the way out of the city at a checkpoint set up by the shura council, which has prevented residents from negotiating without its permission.

"But we told them we have to go, at least we try," said a member of the delegation, who spoke on condition of anonymity. "Maybe we can prevent the offensive."

Abdul-Hamid Jadou, a member of the negotiating group, said neither the fighters nor the government were willing to resolve the problem.

"We, the delegation members, were like a soccer ball," Jadou said. "Everyone kicks it to the other.

Correspondent Karl Vick in Baghdad and special correspondent Omar Fekeiki contributed to this report.

U.S. Marines outside Fallujah bow their heads in prayer as the military prepared for a possible assault on the Iraqi city, which is held by rebels.