President Bush has renewed a threat to veto a bill expanding health insurance for millions of American children. The State Child Health Insurance Program, known as S-CHIP, expires later this month. Lawmakers have proposed to spend $35 billion to cover an additional four million children over the 6.6 million already enrolled. The money would come mostly through a tax increase on cigarettes. The White House wants to limit the increase to just $5 billion. On Thursday, President Bush called the proposed expansion “a step toward federalization of health care” and promised a veto.