The approval followed President Barack Obama's decision to lift restrictions on federal funding for embryonic stem cell research, which President George W. Bush had implemented.
Embryonic stem cells show potential for treating various diseases, because they can develop into many types of tissue. However, actual use of the stem cells has yet to be approved.
Rockefeller University in New York City developed two of the stem cell lines while the Children's Hospital in Boston developed the other 11. The NIH is reviewing 96 lines, some of which may be approved by Friday.
The New York Times reported that opponents of embryonic stem cell research said that researchers should focus on adult cells, which could be reprogrammed to the embryonic state.
Though adult cells induced into the embryonic stage are very similar to actual embryonic stem cells, they are not identical and are riskier to use. The adult cell may turn on its defenses when being forced into the embryonic stage and will be useless to researchers.