President Barack Obama has overturned a ban on federal funding for stem cell research, reversing the policy of his predecessor George W Bush.
Mr Obama said the move would open the door for America to "lead the world" in laboratory work to find cures for a number of devastating diseases and conditions.
In lifting the ban, the President stated that the White House would make scientific decisions "based on facts, not ideology" from now on.
President Bush brought in the ban on federal funding for the use of research on embryonic stem cells in 2001. Supported by religious right, the then President ruled that the procedure was morally wrong.
Opponents to the research object on the grounds that embryos - the early stages of potential life - are destroyed in a bid to obtain stem cells.
But scientists believe that master cells can be used to form the basis of therapies for a number of illnesses and conditions such as Parkinson's disease, Alzheimer's and spinal cord injury.
High-profile supporters of research in the US include Nancy Reagan, whose husband, former President Ronald Reagan, suffered from Alzheimer's, and Parkinson's sufferer Michael J Fox.
The late actor Christopher Reeve, who was paralysed in an accident, campaigned for the ban to be overturned up until his death in 2004.
Mr Obama said that he wished that the Superman actor was alive today to see the ban revoked.
He said that Mr Reeve dreamed of being able to walk again, adding "Christopher did not get that chance. But if we pursue this research, maybe one day - maybe not in our lifetime, or even in our children's lifetime - but maybe one day, others like him might."
The ban on federal cash for research has, the scientific community has long argued, hampered efforts in the US to find cures and therapies to a ride range of conditions.
Mr Obama acknowledged the damage done by the Bush policy, stating that when investment in research is not made: "Opportunities are missed, promising avenues go unexplored, some of our best scientists leave for other countries that will sponsor their work."
He added: "In recent years, when it comes to stem cell research, rather than furthering discovery, our government has forced what I believe is a false choice between sound science and moral values."
As such he signed an executive order lifting the ban on federal money for stem cell research.
But the President said that research would only be supported when it was "scientifically worthy and responsibly conducted".
He said that the government would "never" open the door to human cloning.
"It is dangerous, profoundly wrong, and has no place in our society, or any society," Mr Obama said.
The President said that it was important that scientific data was not used to serve a political agenda. As well as the executive order, Mr Obama signed a memorandum calling for a White House strategy to restore scientific integrity.
This would ensure that the administration would base public policy on the "soundest science" and would not appoint scientific advisers based on politics or ideology.
Today's executive order was welcomed by scientists and campaign groups in the US and further afield.
Rebecca Wood, chief executive of the Alzheimer's Research Trust in the UK, said: "Stem cell research in the UK and Europe has opened some exciting avenues of research into possible treatments for Alzheimer's, and these efforts could now be boosted by greater input from American researchers.
"Since Alzheimer's and other diseases cause the gradual death of brain cells, stem cell research could lead to completely new approaches to tackling dementia focused on replacing lost brain cells. Dementia is a global challenge - affecting 26 million people worldwide - requiring global solutions."
But pro-life groups reacted bitterly.
Douglas Johnson, a spokesman for the National Right to Life Committee, said: "It is a sad day when the federal government will fund research that exploits living members of the human species as raw material for research,"
"Obama's order also places our society on a very steep, very slippery slope."