WASHINGTON — Congress approved legislation yesterday that would potentially add 4 million children to a popular healthcare program, setting up a veto fight that President Bush probably will win but handing Democrats a campaign issue for next year's elections.

Eighteen Republicans in the Senate lined up with Democrats in voting 67-29 to increase spending on the State Children's Health Insurance Program, or SCHIP, from about $5 billion to $12 billion annually for the next five years. Hawai'i Sens. Daniel Akaka and Daniel Inouye voted for the bill.

The vote was enough to override a promised Bush veto. But supporters in the House, which passed the bill Tuesday, are about two dozen votes shy of an override. Both chambers would have to muster two-thirds majorities to win a veto showdown.

Overall, spending for SCHIP would increase to $60 billion over five years in the unlikely prospect the bill becomes law — double what Bush recommended.

Analysts projected the legislation would allow about 4 million of the estimated 9 million uninsured children in the United States to gain coverage.

Bush and most GOP lawmakers say the spending increase is too large and would expand the program beyond its original intent. That intent was to help families with incomes too large to qualify for Medicaid but not enough to afford private insurance.

In a statement after the Senate vote, the White House said Bush "will veto this bill because it directs scarce funding to higher incomes at the expense of poor families."

Opponents of the measure said they support SCHIP, which was enacted a decade ago, and want to renew it before it is set to expire tomorrow. However, they said they could not go along with such a large spending increase.

Republicans braced for criticism that they were being insensitive to low-income children who are uninsured through no fault of their own. They said the legislation was an effort to score political points and another step toward universal healthcare paid for by the government.

"Democrats are counting down the hours so they can tee up the election ads saying Republicans don't like kids," said Senate Minority Leader Mitch McConnell, R-Ky. "Meanwhile, they're using SCHIP as a Trojan horse to sneak government-run healthcare into the states."

Democrats said there was strong public support for expanding the children's healthcare program. They portrayed the president as isolated in his view that the legislation would be a mistake.

"With each passing day, he reveals ever more clearly that the values of his administration are out of touch with those of average Americans," said Sen. Edward M. Kennedy, D-Mass.

The additional spending would be paid for through a 61-cent increase in the federal excise tax on a pack of cigarettes.

Opponents argued during the debate that expanding the program too much would lead to many families dropping private coverage. The Congressional Budget Office has projected that about 2 million children who otherwise would have private insurance would join SCHIP.

Anticipating a veto, Congress will continue funding SCHIP at its current level until mid-November as part of another bill keeping federal agencies in operating funds beyond Sept. 30.