WASHINGTON - President Bush on Friday condemned stem cell research advances in South Korea and said he worried about living in a world in which human cloning was condoned. He said he would veto any legislation aimed at loosening limits on federal support in the United States.

"I'm very concerned about cloning," Bush told reporters in the Oval Office. "I worry about a world in which cloning becomes acceptable."

"I made it very clear to the Congress that the use of federal money, taxpayers' money to promote science which destroys life in order to save life is — I'm against that. And therefore, if the bill does that, I will veto it."

Republicans in Congress are sharply divided over the stem cell issue, which could lead to the first veto of Bush's presidency. The president's comments were aimed at putting the brakes on a bill gaining momentum on Capitol Hill.

That bill would lift Bush's ban on using federal dollars to do research on embryonic stem cell lines developed after August 2001. The president's veto threat drew immediate reaction from sponsors of the bipartisan bill, Reps. Mike Castle, R-Del., and Diana DeGette, D-Colo.

Castle said the legislation would not allow the cloning of embryos or embryo destruction. Instead, it would let government-funded researchers work with stem cells culled from embryos left over from fertility treatments.

"The bottom line is when a couple has decided to discard their excess embryos, they are either going to be discarded as medical waste or they can be donated for research," Castle said.

DeGette protested too. "It's disappointing that the president would threaten to use his first veto on a bill that holds promise for cures to diseases that affect millions of Americans," DeGette said. "Support for expanding federal stem cell research in an ethical manner remains strong in Congress."