Congressional Democrats, having made modest changes to a children's health bill that President Bush vetoed, plan to bring the issue to another vote Thursday in hopes of scoring a win on a top domestic issue.

House Democratic leaders, and key Republicans supporting them, said Wednesday they believe they have altered the measure enough to pick up the handful of GOP members they need to assemble a veto-proof majority, or two-thirds of the House. Republican leaders urged their colleagues to resist, saying the changes are too insignificant to justify abandoning the president on a high-profile issue.

Democrats said they will not know whether they have attracted enough Republican converts until the vote is taken. If enough Republicans again stick with the president, Democrats said, they will pay a political price.

The revised bill "addresses all the concerns that were expressed by our colleagues and by the president," House Speaker Nancy Pelosi, D-Calif., told reporters. "This is a clarification of the legislation" vetoed by Bush.

Moderate Republicans who opposed the veto urged colleagues to embrace the revised bill.

"The reason Congress is held in low esteem is lack of achievement," said Rep. Mike Castle, R-Del. Expanding the health care program, with or without Bush's consent, would be a major accomplishment, he said in an interview.

The proposed changes would not affect the heart of the bill that drew Bush's veto, which the House narrowly sustained last week. The measure still would add $35 billion over five years to the State Children's Health Insurance Program, a figure the administration has called too high. It would enable the program, which now covers 6 million children, to cover 4 million more.

The increase would be paid for with a 61-cent increase in the federal excise tax on a pack of cigarettes. Bush has said he opposes any tax increase.

The proposed revisions, designed to woo a few more Republicans, involve eligibility matters. Families earning more than three times the federal poverty rate would be excluded, except in New Jersey, where a higher threshold could continue at least for a while.

Low-income childless adults, which some states cover, would be phased out in one year. And states would have to be more rigorous in checking the validity of applicants' Social Security numbers, an effort to exclude illegal immigrants.

The 10-year-old health insurance program is designed for families that make too much money to qualify for Medicaid but not enough to buy medical coverage. The main targets are families earning twice the federal poverty rate or less, or $41,300 for a family of four.

The battle over how and how much to expand the SCHIP program has dominated the domestic agenda in recent weeks. Democrats, and some Republicans, feel Bush blundered by vetoing the proposed expansion. Many House Democrats wanted to bring the issue back to the chamber quickly because they feel it is a political winner.

Pelosi rejected requests from several Republicans to postpone a vote in order to give GOP moderates more time to round up support. If Bush vetoes the revised version, Democrats noted, the showdown will occur when supporters seek the two-thirds majority needed for an override. The Senate passed the first proposed expansion by a veto-proof margin, so the House is the focus of the battle.

On Oct. 18 the House voted 273-156 to override Bush's veto of the first proposed $35 billion expansion. That was 13 short of the two-thirds majority needed. Forty-four Republicans joined 229 Democrats in voting to override.

Democrats are targeting three dozen House Republicans who backed the veto and said in a letter they were mainly concerned about eliminating higher-income families, adults and illegal immigrants. "All three issues have been addressed," Rep. Rahm Emanuel, D-Ill., said Wednesday. "Now the question is, can they take yes for an answer."

On Wednesday, Health and Human Services Secretary Mike Leavitt said lawmakers have not justified the need for a $35 billion expansion to cover 10 million children.

"We can't figure out how they get 10 million out of their program," Leavitt told reporters after meeting with senators. "We need to deal with the question of who should be covered by this program, and then do the arithmetic, both on how many children and how much it should cost."

The Center for Children and Families at Georgetown University says 9.4 million American children lack health insurance. Nearly seven in 10 are from families with incomes less than twice the federal poverty level, the center reports.

In an interview, Leavitt said about $10 billion could be shaved from the bill by tightening requirements for applicants to prove citizenship, by more quickly removing adults from the rolls, and by reducing what he described as excessive allotments to states.

"We're bringing ourselves closer on the policy," he said. "But we don't see changes in the specific budget."