WASHINGTON  The Obama administration said Tuesday that it would appeal a court ruling challenging the legality of President Obama’s rules governing human embryonic stem cell research, as the head of the National Institutes of Health said the decision would most likely force the cancellation of dozens of experiments in diseases ranging from diabetes to Parkinson’s.

Officials said experiments already under way could continue. But if the ruling is upheld, the government will be forced to suspend $54 million in financing for 22 scientific projects by the end of September. An additional 60 projects are threatened, and the institutes were busy Tuesday e-mailing researchers to tell them their money was in jeopardy.

“This decision has the potential to do serious damage to one of the most promising areas of biomedical research, just at the time when we were really gaining momentum,” said Dr. Francis S. Collins, director of the National Institutes of Health. The ruling, he added, “just pours sand into that engine of discovery.”

The ruling, issued Monday, revived what had been a dormant moral and political debate over the research just in time for the November midterm elections. At a time when members of both parties are trying to focus on jobs and the economy, thorny questions about the ethics of scientific experimentation were once again percolating in Washington.