WASHINGTON — House Democrats failed Thursday to override President Bush's veto of their pre-election year effort to expand a popular government health insurance program to cover 10 million children.

The bill had bipartisan support but the 273-156 roll call was 13 votes short of the two-thirds majority supporters needed to enact the bill into law despite Bush's objections. The bill had passed the Senate with a bigger than two-thirds majority.

The State Children's Health Insurance Program now subsidizes health care insurance coverage for about 6 million children at a cost of about $5 billion a year. The vetoed bill would have added 4 million more children, most of them from low-income families, to the program at an added cost of $7 billion annually.

To pay for the increase, the bill would have raised the federal tax on cigarettes from 39 cents to $1.00 a pack.

"This is not about an issue. It's about a value," House Speaker Nancy Pelosi, D-Calif., said just before the vote. "For the cost of less than 40 days in Iraq, we can provide SCHIP coverage for 10 million children for one year."

Republican opponents said the bill would encourage too many middle-income families to substitute government-subsidized insurance for their private insurance. The bill gives states financial incentives to cover families with incomes up to three times the federal poverty level — $61,950 for a family of four.

"That's not low-income. That's a majority of households in America," said Rep. Wally Herger, R-Calif.

But Democrats said the bill's original focus would remain intact. States would be given bonuses for signing up low-income children already eligible for the program but not enrolled.

"Under current law, these boys and girls are entitled to their benefits," said Rep. John Dingell, D-Mich. "Continuing to not provide them with coverage is a travesty."

The bill specifically states that illegal immigrants would remain ineligible for the children's program, but Republicans seized on a section that would allow families to provide a Social Security number to indicate eligibility. Rep. Joe Barton, R-Texas, said it's too easy to get a false number, which would give an opening for thousands of illegal immigrants to enroll.