WASHINGTON — The Obama administration is warning that money to fight the Zika virus is on the verge of running out amid political stalemate on Capitol Hill.

The secretary of Health and Human Services says the National Institutes of Health will exhaust its resources for vaccine development by month's end.

The letter from HHS Secretary Sylvia Burwell says that without additional money the second phase of clinical trials will be delayed, and Americans will have to wait longer for a vaccine.

The news comes as the first local transmissions of the virus have been found in Miami and authorities are warning pregnant women to stay away from the area. The virus can cause severe birth defects.

Congress never acted on President Barack Obama's emergency spending request.