The White House will announce a $2.7 billion initiative today to redouble efforts to usher uninsured children into government health programs, even as fresh evidence suggests that enrollment in the most recent of those programs continues to climb.

In the budget he is to release next month, President Clinton will call for the first expansion of the Children's Health Insurance Program (CHIP), which was created in 1997, by giving states the discretion of admitting 19- and 20-year-olds. The expansion could allow as many as 1.2 million more young people to join CHIP, depending on how many states took part, White House officials said.

The administration also is seeking to expand the role of schools in finding children who qualify for either Medicaid, the government insurance program for the poor, or CHIP, which is intended for youngsters in families with incomes too high for Medicaid but too low to afford private insurance.

The administration is proposing that schools be permitted to share with Medicaid workers information about which students are poor enough to qualify for federally subsidized school lunches, much as they can now divulge that information to states' CHIP programs.

In addition, the White House is expanding on a proposal--which received a cool reception in Congress two years ago--that would allow schools and certain other sites to immediately enroll children who seem likely to qualify for the government insurance program while their applications are processed. Such instant eligibility now can be granted only in limited settings, such as hospitals and doctors' offices that accept Medicaid patients, Head Start centers, and federally subsidized nutrition programs.

The administration also wants to require states that have cumbersome enrollment processes for Medicaid to simplify them, in hopes of overcoming one of the reasons why some families do not apply.

The initiative represents a series of modest steps to reduce the number of uninsured children largely by finding those who are eligible for government help but have not taken advantage of it. According to the most recent estimates, 11 million U.S. children lack health insurance, including about 7.5 million whose families have incomes low enough to allow them to qualify for the two government programs.

White House officials also have indicated that the budget Clinton intends to send to Congress on Feb. 7 will include some broader measures to expand health coverage, but they have been sketchy about the details, saying they have not been resolved.

The administration began to spread word of its efforts to enroll more children on the same day the Department of Health and Human Services announced that enrollment in CHIP has increased to 1.98 million for the fiscal year that ended last October--about double the enrollment for the calendar year that ended in Dec. 31, 1998.