SAN FRANCISCO - It's official: The United States has fallen far behind in mining the promising field of stem cell research to treat disease.

A team of South Korean researchers announced Thursday it had successfully harvested stem cells from a cloned embryo - a feat U.S. researchers have been trying to accomplish since at least 2001.

Meanwhile, U.S. scientists complain that a lack of money and a charged political climate have brought the field to a virtual standstill here.

Many researchers believe creating stem cells by cloning embryos in labs may eventually create therapies that won't lead to immune rejection problems in people.

U.S. scientists hailed the announcement as a landmark occasion but also lamented that a technology largely created in the richest nation on earth was getting more support abroad.

Singapore in November unveiled "Biopolis," a $287 million government biotech center focused on stem cell research.

Chinese researchers last year reported fusing human skin cells with rabbit eggs to produce early-stage embryos, which in turn yielded stem cells. The government is also building a stem cell research center.

England, Israel and several other countries also have more advanced stem cell programs.

Those countries aren't as politically riven by the issue as the United States.

Some Christian and politically conservative groups oppose the research - especially cloning - as immoral because fertilized embryos must be destroyed to harvest the stem cells. Leon Kass, chairman of the President's Council on Bioethics, on Thursday called on Congress to ban all forms of cloning.

Chief among the U.S. scientists' complaints is the relative lack of money devoted to such research. The federal government limits what researchers can work on with taxpayer-funded grants. The Bush administration policy also forbids federal funding of all cloning research, even if the projects are intended solely to create stem cells like the South Koreans did.

"All the money for this work has dried up," said Dr. Robert Lanza of Worcester, Mass.-based Advanced Cell Technology, the one U.S. company that has publicly attempted to clone for stem cells, albeit unsuccessfully. "We are lucky to still be in business. Our research has suffered immensely."

Lanza said he's been unable to work with human embryos since October because of the high cost of obtaining eggs and the company's desperate need for investment.