BAGHDAD, Iraq — Iraqis were divided Wednesday over President Bush's rejection of a timetable for the withdrawal of American troops, which came as insurgents bent on starting a civil war blew up a natural gas pipeline and killed a police officer.

A former Sunni Arab Cabinet minister also formed a political front to represent the demands of an umbrella group of insurgents demanding a timetable for U.S. troop withdrawal and an end to all military offensives in Iraqi cities.

The U.S. military also said a mortar attack in the northern town of Tal Afar had killed four Iraqis, including a child, late Tuesday.

An explosion thought to be the work of saboteurs damaged a natural gas pipeline linking storage facilities in Yousfiyah, south of Baghdad, to one of two plants where the gas is bottled in the capital. The extent of the damage was unclear and it was not known if it would lead to a shortage. Most people in Baghdad use gas for cooking.

Gunmen killed police Lt. Jasim Mahmoud and wounded another officer north of Baghdad near the city of Baqouba on Wednesday, police Lt. Col. Ahmed Khamis said.

Bush's speech marking the first year of Iraq's sovereignty was broadcast live on several Arab television networks. But most Iraqis were asleep because it began about 4 a.m. local time Wednesday. TV newscasts replayed part of it later, drawing a wide range of reactions.

"Iraq cannot be stable if the American and coalition forces left it because Iraqi forces don't have the required level of training to protect the country," said Baghdad University engineering professor Moayad Yasin al-Samaraie, 55.

But other Iraqis still believe the presence of about 138,000 U.S. troops is an occupation force preventing local officials from fully controlling internal affairs.

"The transfer of authority was a great dream but nothing took place," said Samah Abdul Mihsen, a 24-year-old housewife living in al-Amin al-Thaniyah, a middle-class neighborhood in eastern Baghdad. "Bush does not want to pull out the American forces although we can defend our country. There are so many problems because of the presence of foreign troops."

Those problems include a failure to fully restore basic services, such as electricity, water and sewage treatment.

"Bush's speech does not change anything for the Iraqi people and does not meet their needs for water, electricity, transportation and security from car bombs. I think the Iraqi people do not care about the speech because they are so preoccupied with their daily needs," said Mahmoud Othman, a Kurdish member of parliament.