President Bush has renewed a threat to veto a bill that would extend health insurance to more than three million low-income children. Last week, senators reached a bipartisan agreement to add $35 billion to the Children’s Health Insurance Program over the next five years by increasing federal taxes on cigarettes. Senators say the extra funding would help cover some of the nation’s eight million uninsured children as well as some adults with incomes too high to qualify for Medicaid but not high enough to afford private insurance. President Bush wants Congress to limit the increase to just $5 billion.