BAGHDAD — Guards in a security convoy opened fire on a car at an intersection in central Baghdad on Tuesday, killing two Christian women before speeding away, police said. The Iraqi government said a Dubai-based private security company was behind the shootings.

Interior Ministry spokesman Maj. Gen. Abdul-Karim Khalaf said the Unity Resources Group had apologized after guards in four SUVs fired on a car carrying the two women, killing them instantly.

Khalaf said the government and the company have both begun investigations and that initial findings showed the guards fired 19 bullets.

"They apologized and said they are ready to meet all the legal commitments," he said.

Unity Resources Group, which has operated in Iraq since 2004, employs security professionals from the U.S., Britain, Australia and New Zealand.

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Romney, Giuliani face off on taxes, spending

DEARBORN, Mich. — Republican presidential hopefuls Mitt Romney and Rudy Giuliani clashed over tax and spending cuts Tuesday, each claiming greater commitment than the other in a debate in the nation's struggling manufacturing heartland.

The government "is spending money of future generations and those yet to be born," added Fred Thompson, making his debate debut after a late entry into the race. He said future retirees should receive smaller Social Security benefits than they have been promised.

After months of polite debate sparring, Giuliani and Romney squared off without hesitation, a reflection of their struggle for primacy in the race for their party's presidential nomination.

"I cut taxes 23 times. I believe in tax cuts," said Giuliani, former mayor of New York and leader in national Republican polls.

Romney in turn criticized his rival for once filing a court challenge to a law that gave President Clinton the right to veto spending items line by line. "I'm in favor of the line item veto," he said, adding he exercised it 844 times while governor of Massachusetts.

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Group: US officials leaked secret info on al-Qaida video

NEW YORK — The director of a group that monitors Islamic militant Web sites said the government leaked an Osama bin Laden video that was passed along to senior U.S. officials on condition that they keep it secret. She claimed the leak rendered certain intelligence-gathering capabilities ineffective.

The White House said it was not responsible for the leak, and a senior official said the director of national intelligence should investigate the allegation.

Rita Katz, who runs the Washington-based SITE Institute, said her decision to pass the video to an official in the Bush administration has had an impact on the ways that the group has for obtaining these videos before they are made available by al-Qaida.

"Due to the leak, sources that took years to develop are now ineffective," Katz told The Associated Press on Tuesday. "A rare window into the world of al-Qaida has now been sealed shut." She declined to elaborate on whether she meant people or methods.

In a story first reported by The Washington Post on Tuesday, Katz said that on Sept. 7 she contacted White House counsel Fred Fielding, whom she had met before and trusted, and offered the video and a transcript, long before anyone else had a copy.

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Pentagon panel wants nuclear security tightened

WASHINGTON — The U.S. government should replace more than 1,000 irradiation machines used in hospitals and research facilities because terrorists could use the radioactive materials inside to make a "dirty" bomb, a government advisory panel has concluded.

"Any one of these 1,000-plus sources could shut down 25 square kilometers, anywhere in the United States, for 40-plus years," according to panel documents obtained by The Associated Press.

The machines are in relatively unprotected locations such as hospitals and research facilities all over the country, and may be a tempting source of radioactive materials for terrorists who want bombs that explode and disperse radioactive debris over a large area, rendering it uninhabitable, the board found.

The irradiators contain Cesium-137, one of the most dangerous and long-lasting radioactive materials. They are used for radiation therapy and to sterilize blood and food.

Swapping the Cesium irradiators for X-ray machines or irradiators that use other materials would cost about $200 million over five years, but it would take the most accessible source of dangerous radioactive material inside the United States "off the table" for terrorists, the panel says.

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Hillary Rodham Clinton proposes 401(k)s

WEBSTER CITY, Iowa — Democratic presidential candidate Hillary Rodham Clinton proposed tax cuts of up to $1,000 a year on Tuesday to encourage millions of working-age families to open personal 401(k) retirement accounts.

The New York senator said the program would be paid for through higher estate taxes.

At the same time, Clinton said she has given up another idea for a savings incentive — giving every baby born in the United States a $5,000 account to pay for college or a first home.

Instead, she said, her plan for what she called "American Retirement Accounts" will provide "universal access to a generous 401(k) for all Americans."

She outlined a program in which the government would provide a "matching refundable tax credit — dollar for dollar — for the first $1,000 of savings done by every married couple making up to $60,000 a year."

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Deputy died from gunshot wound to the head

CRANDON, Wis. — An off-duty sheriff's deputy who killed six people apparently shot himself three times, with the last shot hitting him in the right side of the head, the state attorney general said Tuesday.

Tyler Peterson, 20, shot himself twice under the chin, while the third and fatal shot entered the right side of his head, Attorney General J.B. Van Hollen said. Peterson also was shot once in the left biceps from a distance.

The six people who died were either students or recent graduates of Crandon High School, where Peterson also had graduated. They were at the house to share pizza and watch movies during the school's homecoming weekend when Peterson attacked early Sunday.

The lone survivor was scheduled for surgery Tuesday afternoon.

Peterson died near a friend's home in Argonne.

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Molson Coors, SABMiller plan to combine U.S. operations

MILWAUKEE — The nation's second and third-largest brewers, Miller and Coors, are planning to blend their U.S. operations to help them compete in a struggling U.S. industry and against its leader, Anheuser-Busch.

The deal, announced Tuesday, will place almost 80 percent of the U.S. beer market in the hands of just two companies, the new MillerCoors and Anheuser-Busch, making it a likely target for a tough antitrust review.

Miller Brewing Co., owned by SABMiller PLC, has about 18 percent of the market, as of last year, according to trade publication Beer Marketer's Insights. Molson Coors Brewing Co. has almost 11 percent and Anheuser-Busch Cos. has just under half the market.

The companies said the combination will have to pass an antitrust review by either the Federal Trade Commission or the Department of Justice.

Few analysts expect the government to try to block the deal, however, despite close scrutiny by regulators.

Supermarkets and restaurants — two large buyers of beer — will play a large role in the review, said Veronica Kayne, an attorney at Haynes & Boone and former FTC antitrust official.

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Study: post-menopausal women who cut dietary fat may reduce risk of ovarian cancer

WASHINGTON — Cutting dietary fat may also cut the risk of ovarian cancer, says a study of almost 40,000 older women that found the first hard evidence that menu changes protect against this particularly lethal cancer.

But don't wait too long to get started: The protection didn't kick in until the women had eaten less fat for four years and counting.

Until now, the only known prescription against ovarian cancer — aside from surgically removing the ovaries — was to use birth control pills. Use for five years can lower the cancer risk by up to 60 percent, protection that lingers years after pill use ends.

The new findings now offer an option for postmenopausal women to try as well.

Those who followed a low-fat diet for eight years cut their chances of ovarian cancer by 40 percent, researchers reported Tuesday in the Journal of the National Cancer Institute.

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Lohan says staying sober is her main priority

NEW YORK — Lindsay Lohan is making plans for life after rehab. The 21-year-old actress reportedly checked out of the Cirque Lodge, a drug and alcohol treatment center in Utah, on Friday. She had entered treatment in August after reaching a plea deal on misdemeanor drunken driving and cocaine charges following two arrests.

"It was a sobering experience," Lohan says in an interview with OK! magazine. "It was humbling. It made me look at myself, and all of the people, places and things in my life in a different way. I was in there for substance abuse, after all."

Staying sober — and out of Los Angeles — is Lohan's main priority.

"I'm staying in Utah until it's time to shoot `Dare to Love Me,' and then I plan on returning to Utah so I can stay focused, and avoid other distractions," she tells OK!