WASHINGTON (CNS) -- With the rapid advances in medicine, science and technology, beginning-of-life issues that seemed a remote possibility in 2000 have emerged as hot political topics in 2004.

In the forefront are human cloning and stem-cell research using human embryos. Human cloning, at least of embryos, is now a laboratory reality.

On both issues, President George W. Bush and U.S. Sen. John F. Kerry of Massachusetts, his Democratic opponent in the November presidential election, have sharp differences.

The June 5 death of former President Ronald Reagan, who suffered from Alzheimer's disease, revived the political debate over federal funding of human embryonic stem-cell research, which de facto destroys the embryos.

The debate surfaced even as many scientists favoring such research said stem cells hold out little hope for Alzheimer's patients, but offer promise in the fight against other major illnesses such as heart disease, diabetes and Parkinson's disease.

As president, Bush has restricted federal funding of human embryonic stem-cell research to those lines in existence on Aug. 9, 2001, the date he announced the policy. Kerry favors relaxing these rules to allow federal funding of research using embryonic stem-cell lines developed after the Bush deadline.

In an Aug. 7 radio address, Kerry called the Bush administration "one of the most anti-science administrations in our nation's history" and said that as president he would "stand up for science."

"At this very moment, some of the most pioneering cures and treatments are right at our fingertips, but because of the stem-cell ban, they remain beyond our reach," Kerry said. "That is not the way we do things in America. Here in America, we don't sacrifice science for ideology."

In response, Bush said his administration was the first to actually fund stem-cell research, with his 2003 budget including $24.8 million for research on the existing embryonic stem-cell lines and $190 million in funding for adult stem cells.

"The principle that human embryos merit respect as a form of human life -- and that the federal government should not encourage their destruction -- has been accepted on a bipartisan basis for a number of years," says a fact sheet on the Bush campaign Web site. "Every year since 1996, Congress has adopted legislative language stating that federal funds may not be used in research involving the destruction of human embryos."

Regarding cloning, Bush has said he would sign legislation banning all human cloning. A total ban bill has passed the House of Representatives and a similar bill is in the Senate. Kerry supports a rival Senate bill that would ban cloning for human reproduction but would allow the cloning of human embryos for medical research.

While the bishops do not endorse candidates, they take stands on issues.

In their 2003 voter guideline document, "Faithful Citizenship: A Catholic Call to Political Responsibility," the bishops based their opposition to human embryonic stem-cell research and human cloning on the principle that human life begins at conception.

"The destruction of human embryos as objects of research is wrong. This wrong is compounded when human life is created by cloning or other means only to be destroyed," said the bishops' document.

"We call on government and medical researchers to base their decisions regarding biotechnology and human experimentation on respect for the inherent dignity and inviolability of human life from its very beginning, regardless of the circumstances of its origins," it says.

Regarding human cloning, separate statements by church officials have supported the total ban contained in a bill that passed the House in 2003 and in a Senate bill sponsored by Sen. Sam Brownback, R-Kan. Bush supports both bills.

Kerry supports a rival Senate bill sponsored by Sen. Orrin Hatch, R-Utah, which would ban cloning for human reproduction but allow it for research purposes, said Andy Davis, a spokesman in Kerry's Senate office.

Catholic bioethicists have noted that the church's opposition to using embryonic stem cells is not a hindrance to research. They cite research with adult stem cells as more promising, since embryonic stem cells are said to be more unstable.

Stem cells are basic cells capable of transforming themselves into the specialized cells present in specific body organs. Currently, embryonic stem-cell research involves embryos created in vitro by uniting a sperm and egg in a laboratory.

Supporters of embryonic research say stem cells from embryos can be transformed into more types of specialized cells than adult stem cells can.

Many supporters of embryonic research also favor legalizing the cloning of human embryos solely for research purposes to provide more cells for investigation. This type of cloning is often called "therapeutic cloning."

John M. Haas, president of the National Catholic Bioethics Center in Boston, said the church opposes "therapeutic cloning" because it still involves destroying human embryos in the research.

Haas also noted that Bush's restrictions on federal funding of embryonic stem-cell research do not prohibit private funding of such research.

But private funds have not been plentiful because there are "not enough positive results on embryonic stem-cell research for venture capitalists," said Haas. "It doesn't hold out nearly the promise as adult stem cells."

Haas said a main reason behind Bush's restriction of federal funding to previously existing cell lines was that "he didn't want any more embryos destroyed."

The bishops' stem-cell stand is having an influence on Catholics, according to a recent survey.

A Le Moyne College/Zogby International poll released July 7 showed that 73 percent of Catholics surveyed support adult stem-cell research and 63 percent oppose using embryonic stem cells. The margin of error was plus or minus 2.7 percent.

"In that regard, they're not that different than the general public whose support overall is stronger for adult stem-cell research," said Theresa Beaty, chemistry and physics professor at Le Moyne College in Syracuse, N.Y.