Oct 28 (Reuters) - Citigroup Inc (C.N) said on Thursday it will require all U.S. employees to be vaccinated against COVID-19 as a condition of their employment. The bank will comply with the Biden administration policy requiring all workers supporting government contracts to be fully vaccinated, as the government remains a "large and important" client of Citi, said Sarah Wechter, head of human resources, in a LinkedIn post. However, the bank said it will assess exemptions on religious or medical grounds, or any other accommodation by state or local law, on a case-to-case basis. Big Wall Street institutions have been grappling with questions around employee safety and how to bring back workers, as the highly infectious Delta variant of the coronavirus spread across the country. While some firms have pushed back their return-to-office plans, others have chosen to stay the course. Earlier this month, Bank of America Corp (BAC.N) said it will pay out $200 awards to its employees at Merrill Lynch Wealth Management who are fully vaccinated and going to office regularly.