Aside from Katrina relief, there is no more urgent and important piece of unfinished business before the Senate this fall than a vote on H.R. 810, the Stem Cell Research Enhancement Act. Further delay in bringing this to a vote is intolerable. People are dying from diseases and medical conditions that might be cured through embryonic stem-cell research. For these people, every month matters. And every day of delay by the Senate has life-and-death consequences.

In poll after poll, the overwhelming majority of Americans support embryonic stem-cell research. Here in Congress, H.R. 810 passed the House last spring with a strong bipartisan majority; its identical counterpart in the Senate, sponsored by Sen. Arlen Specter (R-Pa.) and me, also is supported by a strong bipartisan majority in the Senate.

In a dramatic speech on the Senate floor in late July, Specter announced his personal support for the bill, explaining that he no longer thinks the administration’s policies enable scientists to pursue the “truly magnificent, truly remarkable properties” of stem cells taken from days-old human embryos. Yet we are still denied a vote.

Our nation’s top scientists are eager to go forward with embryonic stem-cell research. By studying how stem cells are transformed into the whole gamut of specialized cells (muscle cells, heart cells, etc.), scientists expect to gain valuable insights into the processes that lead to Parkinson’s disease, cancer and other medical conditions. In addition, they expect that embryonic stem cells could offer an endlessly renewable source of replacement cells and tissues for treating everything from burns to spinal cord injuries to osteoarthritis.

Today, however, much of this promise and potential is at risk. We now know that all 22 stem-cell lines available under President Bush’s restrictive policy are contaminated with mouse feeder cells, making them dangerous for use in humans. Since the president announced his policy, arbitrarily banning stem-cell lines created after Aug. 9, 2001, scientists have made great advances in deriving stem-cell lines. Many of the new lines were grown without mouse feeder cells.

As a consequence, the United States — the world’s leader in biomedical research — is being left behind as Great Britain, Singapore and South Korea move forward aggressively with embryonic stem-cell research. I recently talked with Dr. Woo Suk Hwang, the world’s leading scientist in this field. He is dismayed that his peers in the United States have been left on the sidelines because of the administration’s restrictive policies.

Shouldn’t our top scientists be allowed to study new embryonic stem-cell lines? We don’t require our astronomers to explore the heavens with 19th century telescopes, and we don’t require our geologists to study the Earth with a tape measure. If we are serious about realizing the promise of stem-cell research, our biomedical researchers need access to the best stem-cell lines available, as long as they meet stringent ethical requirements.

Our aim is to pass H.R. 810 without amendments, so we can send it directly to the president’s desk. But there’s a problem. The White House opposes this legislation, and powerful Republicans are maneuvering to kill the bill. To that end, they are trying to muddy the waters. They want the Senate to vote on six, seven or more bills, some of which have nothing to do with stem-cell research.

Their strategy is to convince Senators that instead of supporting H.R. 810, they can vote for a different bill that promotes alternative methods of deriving stem cells. They figure that if they can peel off enough Senators from H.R. 810, this will keep us from getting the 60 votes we need to stop a filibuster.

Let’s be clear: These alternative approaches are currently nothing but theories. They are hypothetical, speculative and totally unproven. By contrast, we know how to derive embryonic stem cells.

None of the additional stem-cell lines would require the creation of new embryos. These lines could be derived from any of the more than 400,000 embryos left over from fertility treatments — embryos that would otherwise be discarded. The choice before us is to discard unwanted embryos as medical waste, or to use them in research to cure diseases and save lives. It is the second choice, I believe, that is truly respectful of human life.

Should we pursue the various alternative methods? Of course we should. But it is foolish to impede medical research on existing human embryonic stem-cell lines while these more speculative methods are explored.

As I write this, people we love are dying from Parkinson’s and Amyotrophic Lateral Sclerosis. Children are suffering from juvenile diabetes. People are unable to walk due to spinal cord injuries. These people don’t have 10 years to wait and see if alternative methods pan out. They need help now.

At a public rally supporting H.R. 810, actor Michael J. Fox, who has Parkinson’s disease, was asked what advice he would give to Bush on H.R. 810. His answer was: “Carpe diem” — seize the day.

For millions of Americans, this is a matter of life and death. They can’t wait any longer for our top scientists to realize the full potential of stem-cell research. There is no excuse for further delay in the Senate. We must have a vote on H.R. 810 this fall.

Sen. Tom Harkin (D-Iowa) is a member of the Health, Education, Labor and Pensions Committee.