Marking the 34th anniversary of the Roe v. Wade Supreme Court decision that legalized abortion, President Bush thanked thousands of anti-abortion marchers Monday for continuing to demonstrate against the ruling.

"It is important for all Americans to remember that our Declaration of Independence states that every person has a right to life, liberty and the pursuit of happiness," Bush said via a phone call broadcast to participants in the annual March for Life on the National Mall.

Bush pointed to efforts made during his administration to reduce abortions, including expanding adoption, pursuing parental notification laws and stopping federal funding for abortions overseas. He added that his record on "building a culture of life" will continue with ongoing opposition to federal funding of additional embryonic stem-cell research, a key goal of the Democratic-led Congress.

Earlier this month, House Democrats voted to expand federal funding in a bill similar to one vetoed by the president last spring. Bush has pledged to use his second veto on this bill if it passes the Senate and comes to his desk. Democrats do not appear to have the support to override it.

"Our challenge is to make sure that science serves the cause of humanity instead of the other way around," the president said in a telephone call piped over loudspeakers to a Washington rally of opponents of abortion rights. "I have made clear to the Congress, we must pursue medical advances in the name of life, not at the expense of it."

The president, speaking from Camp David, Md., where he spent the weekend finishing up his State of the Union address, encouraged the audience to continue to persuade more Americans to join their cause.

"As we move forward, we've all got to remember that a true culture of life cannot be built by changing laws alone. We've all got to work hard to change hearts," Bush said. "The sanctity of life is written in the life of all men and women. And so I think, go forth with confidence that a cause rooted in human dignity and appealing to the best instincts of our citizens cannot fail."

The Associated Press contributed to this report.