President Barack Obama on Tuesday called for the rapid development of tests, vaccines and treatments to fight the mosquito-transmitted Zika virus, which has been linked to birth defects and could spread to the United States in warmer months.

U.S. health officials are stepping up efforts to study the link between Zika virus infections and birth defects, citing a recent study estimating the virus could reach regions where 60 percent of the U.S. population lives.