Republican presidential Candidate Sen. John McCain, R-Ariz., left, and Democratic presidential candidate Sen. Barack Obama, D-Ill., shake hands during the Compassion Forum at the Saddleback Church on Saturday in Lake Forest, Calif. Host Rick Warren is seen at center.

LAKE FOREST, CALIF. ? Presidential contenders Barack Obama and John McCain differed sharply on abortion Saturday, with McCain saying a baby’s human rights begin “at conception,” while Obama restated his support for legalized abortion.

Appearing on the same stage for the first time in months, although they overlapped only briefly, the two men shared their views on a range of moral, foreign and domestic issues as they near their respective nominating conventions.

Obama said he would limit abortions in the late stages of pregnancy if there are exceptions for the mother’s health. He said he knew that people who consider themselves pro-life will find his stance “inadequate.”

He said the government should do more to prevent unwanted pregnancies and to help struggling new mothers, such as providing needed resources to the poor, and better adoption services.

McCain expressed his anti-abortion stand simply and quickly, saying human rights begin the instant a human egg is fertilized. McCain, who adopted a daughter from Bangladesh, also called for making adoption easier.

The men’s comments came at a two-hour forum on faith hosted by the minister Rick Warren at his megachurch in Orange County, Calif. Obama joined Warren for the first hour, and McCain for the second. The two candidates briefly shook hands and hugged each other during the switch. McCain said he did not see or hear Obama’s session, which would have given him an advantage.

Obama said America’s greatest moral failure is its insufficient help to the disadvantaged. He noted that the Bible quotes Jesus as saying “whatever you do for the least of my brothers, you do for me.” He said the maxim should apply to victims of poverty, sexism and racism.

McCain said the nation’s greatest moral shortcoming is its failure to “devote ourselves to causes greater than our self-interests.”

After the September 2001 terrorist attacks, McCain said, there should have been a national push for joining the Peace Corps and other volunteer organizations.

His comment seemed an indirect criticism of President Bush, who had urged tax cuts and more shopping at the time to stimulate the economy.

McCain also said he would pursue Osama bin Laden “to the gates of Hell,” another goal that might be seen as a swipe at the Bush administration.

Both men said marriage is a union between a man and a woman. Obama added that he supports civil unions for gay partners, which would give them rights such as hospital visits with one another. He said he opposed a constitutional ban on gay marriage, calling the matter a state issue.

McCain’s answer was less clear. If a federal court ordered his state, Arizona, to honor gay marriages allowed in Massachusetts, he said, “then I would favor a constitutional amendment. Until then, I believe the states should make the decisions within their own states.”

In several cases, Obama gave a Christian interpretation to his generally liberal political views. He said he is redeemed by Jesus, who died for his sins.

McCain tended to give shorter, less complex answers, winning somewhat more applause than Obama from the large, evangelical church’s audience. On domestic matters, he restated his call to “drill now” in U.S. lands and waters for oil and natural gas.

McCain, asked the toughest decision in his life, cited his refusal to be released ahead of fellow U.S. prisoners of war in North Vietnam. “It took a lot of prayer,” he said.