Anti-abortion activists went on tactical alert a week ago at news that the Clinton Administration's proposed national health care package would include coverage for elective abortions.

"Any plan that puts abortion into the national health care system will . . . force (House) members from the undecided column into the opposed column," said David Kush, a spokesman for abortion opponent Rep. Christopher H. Smith (R-N.J.).

"We would strongly oppose any mandate . . . that compelled employers, health care providers and citizens to collaborate in abortion on demand," agreed Douglas Johnson of the National Right to Life Committee.

Fighting words.

But an informal survey of major private insurance companies confirms that abortion is already a firmly entrenched benefit. To offer it in a national health care plan would simply continue what already exists in plans that many Americans tap into every day.

What's more, most health care experts now believe that abortion must be part of a broad spectrum of female reproductive health services, all taken in context if the health of women is to be maintained--and health care costs contained. (More women enter hospitals to have babies or to care for reproductive problems than the total number of men who enter hospitals for any reason, a recent survey revealed.)

And employers, insurance companies and ordinary citizens may already "collaborate" in abortion on demand, analysts say.

According to figures from the Alan Guttmacher Institute, a nonprofit public education group, more than 50% of all pregnancies among American women are "unintended;" one half of those pregnancies are terminated by abortion. And nine out of 10 abortions take place in clinics or doctors' offices.

Who pays for all this? In California and 11 other states, Medicaid-eligible women can terminate pregnancy with costs paid by state funds. Nationwide, private insurance--through either group or individual policies--pays for much of the rest.

But nobody knows exactly how many abortions are paid for by private insurance, probably because the issue is such a political hot potato and no one wants to keep tabs.

Said Richard Coorsh, of the Health Insurance Assn. of America: "Nobody knows the extent to which employers offer reproductive rights coverage."

Each employer designs a plan based on what is affordable and wants to offer to employees, Coorsh said. So most plans differ from one another.