President Bush said yesterday that the easy availability of abortions challenges the basic value Americans place on life and urged that alternatives such as adoption be encouraged.

"The prevalence of abortion on demand in America calls into question our respect for the fundamental right to life," he said in a proclamation declaring next Sunday "National Sanctity of Human Life Day."

Bush opposes abortion, except when the mother's life is in danger, but has disappointed antiabortion activists by failing to put it high on his agenda.

"While sincere persons may disagree, my position is that the lives of both must be cherished and protected," Bush said. "We must recognize the dignity and worth of every human being in our laws, as well as in our hearts."

Bush urged Americans to turn to "loving alternatives" to abortion, such as offering babies for adoption. "All levels of government and all sectors of society should promote policies that encourage alternatives such as adoption and make adopting easier for families who want children and will give them loving homes, particularly children with special needs," he said.

Tuesday marks the 18th anniversary of the Supreme Court's ruling that women have a constitutional right to seek abortions.