By ROBERT PEAR

---

WASHINGTON, July 24 - Republican leaders of the House and Senate on Tuesday attacked proposals that call for a major expansion of the Children's Health Insurance Program, to be financed with higher tobacco taxes.

"Republicans will fight these proposals," said the House Republican leader, Representative John A. Boehner of Ohio.

In an unexpected turn of events, the top two Republicans in the Senate, Mitch McConnell of Kentucky and Trent Lott of Mississippi, said they opposed a bipartisan bill that the Senate Finance Committee approved last week and would offer an alternative on the Senate floor.

House Democrats announced their proposals on Tuesday night and estimated that they would provide coverage for five million children who are now uninsured. The Senate bill is expected to cover 3.2 million children.

Top House Republicans objected to the House Democrats' plan to finance their proposals, with increases in tobacco taxes and cuts in subsidies for private health plans serving older Americans on Medicare. Republicans say public coverage would in some cases replace private insurance.

"Dragging people out of private health insurance to put them into a government-run program is 'Hillary care' come back," Mr. Boehner said, referring to the Clinton administration plan for universal coverage.

House and Senate members are working on separate bills to expand coverage for children. Democratic leaders said they hoped that both chambers would approve the bills next week, before Congress begins a monthlong summer recess.

The House bill, developed entirely by Democrats, would increase spending on children's coverage by $50 billion over five years, providing a total of $75 billion.

The bill approved by the Senate Finance Committee, 17 to 4, calls for an increase of $35 billion, for a total of $60 billion.

In a letter to colleagues, Mr. McConnell and Mr. Lott said that the measure "imposes an open-ended financial burden on American taxpayers and takes a significant step toward a government-run health care system."

Six Republicans voted for the bill. Mr. McConnell said other Republican senators were concerned about "the size of the plan that came out of the Finance Committee and what that may portend for the future in terms of an entire government takeover of American health care and, in essence, a single-payer system down the road."

Representative Diana DeGette, Democrat of Colorado, a leading proponent of the House bill, said: "For the longest time, I was mystified why Republicans would oppose expansion of the Children's Health Insurance Program to kids who are eligible but not enrolled. Now I realize. They are trying to deny us a political victory. They want to be able to say that Democrats can't get anything done.

"Unfortunately," Ms. DeGette said, "Republicans are pursuing this strategy on the backs of poor children."

The Senate bill focuses on coverage for children. The House bill also calls for major changes in Medicare. It would, for example, halt a 10 percent cut in payments to doctors, scheduled for January, and would reduce payments for private insurance known as Medicare Advantage plans. Medicare typically pays the private plans more than it would cost to care for the same people in traditional Medicare. Many private plans offer additional benefits.

America's Health Insurance Plans, a trade group, announced a national television advertising campaign. The ads will urge older people to contact their members of Congress and speak out against the proposed cuts in payments to private insurers.