WASHINGTON, Sept 21 (Reuters) - Two major U.S. retail industry groups on Tuesday asked the Biden administration for at least 90 days before imposing new rules that will require employees at larger firms to be vaccinated against COVID-19 or submit to regular testing. On Sept. 9, the White House said the Occupational Safety and Health Administration (OSHA) is developing an emergency temporary standard that will require all employers with 100 or more employees to ensure their workforce is fully vaccinated, or require any workers who remain unvaccinated to produce a negative COVID-19 test once a week. The White House has said those rules will apply to more than 80 million private sector employees. The Retail Industry Leaders Association and the National Retail Federation strongly encouraged OSHA "to provide a 90-day implementation timeline to allow retailers and other employers to create the systems necessary." The retail groups, which represent companies including Walmart (WMT.N), CVS (CVS.N) Best Buy (BBY.N), Target (TGT.N), Kroger (KR.N) and Home Depot (HD.N), asked how the administration will ensure adequate COVID-19 testing capacity to satisfy the "significant increase in demand." The groups said "there could be as many as 4 million retail workers who may need to be tested on a weekly basis." They also asked other detailed questions like "what remedial actions can be taken in situations in which employees refuse vaccinations and testing?" U.S. Commerce Secretary Gina Raimondo told travel executives last week that the OSHA order is expected in "a matter of weeks. ... We have been told in October."