President Bush used his weekly radio address to call for a Constitutional amendment banning gay marriage. Senators opened debate on the measure this past week, after several states began allowing same-sex marriages.

President Bush wants to change the Constitution, because he says a few activist judges are redefining marriage to include unions between two men or two women. That, he says, undermines civilization's most fundamental institution.

"If our laws teach that marriage is the sacred commitment of a man and a woman, the basis of an orderly society, and the defining promise of a life, that strengthens the institution of marriage," said President Bush. "If courts create their own arbitrary definition of marriage as a mere legal contract, and cut marriage off from its cultural, religious and natural roots, then the meaning of marriage is lost, and the institution is weakened."

The president says a constitutional amendment should never be undertaken lightly, but the difficult debate was forced on the country by what he says are activist judges imposing their arbitrary will on the people.

There are already 38 states with laws banning same-sex marriages and a federal statute preventing such marriages in one state from being legal in another. But Mr. Bush warns those laws could be overturned, so the only alternative left to the people, he says, is the only law courts cannot overturn.

President Bush says traditional marriage is critical to the health of society and the well-being of families, which he says pass along values and shape character.

Mr. Bush is pushing to make values a bigger part of the campaign as another way to differentiate himself from presumptive Democratic challenger John Kerry.

Campaigning in the key electoral state of Pennsylvania Friday, the president mocked Senator Kerry for claiming to have conservative values. On issues ranging from funding U.S. troops to reproductive rights to giving federal funds to religious charities, Mr. Bush said, the Massachusetts Senator is out of step with the mainstream values so important to the country and its families.

Senator Kerry responded that values are not words but the way you live and carry out decisions on such issues as budget, education, health care and taking the country to war.

Senator Kerry's running mate, North Carolina Senator John Edwards, kept up the values debate in the Democratic radio address. Senator Edwards said the Bush administration has been slow to prosecute corporate criminals, including a former long-time financial supporter of the president, who was indicted this past week in connection with one of the biggest corporate bankruptcies in U.S. history.

"It took three long years to see Ken Lay handcuffed and indicted for what he did," said John Edwards. "In November, middle-class families will be able to rest assured that John Kerry will look out for their interests, restore corporate responsibility and put our economy back in line with our values."

Mr. Lay has pleaded not guilty to all 11 criminal counts connected with the collapse of the energy firm, Enron. The company, its employees, and their relatives gave more than $500,000 to then Texas Governor George Bush. The White House has distanced itself from Mr. Lay, calling him a former supporter.