The World Health Organization(WHO) has called for a halt in COVID-19 booster shots at least until the end of September to resolve an imbalance in vaccines between rich and poor countries. 

WHO Director-General Tedros Adhanom Ghebreyesus said in a virtual press briefing on Wednesday that more than 80 percent of the four billion doses administered globally have gone to high- and upper middle-income countries, which make up less than half of the world's population. 

He said he understands governments' need to protect against the delta variant, but stressed the WHO's goal set in May to vaccinate at least ten percent of the population of each country by the end of September. 

The U.S., which is considering booster shots for the vulnerable population, rejected the WHO's call. 

White House spokesperson Jen Psaki said in a press briefing on Wednesday that the U.S. "can do both," meaning that it can give booster shots as well as ensure that poorer countries get more vaccines.