On his first day in office, Biden announced that the U.S. will rejoin the Paris Agreement and the WHO.
The $4 billion in US funding was approved by Congress in December and will be distributed through 2022.
"In close cooperation with Gavi, this additional $2 billion in funding will serve to expand Covax's reach", the White House note said.
French President Emmanuel Macron, in an interview Thursday with the Financial Times, called on the US and European nations to allocate up to 5% of current vaccine supplies to developing countries - the kind of vaccine diplomacy that China and Russian Federation have begun deploying.
In an analysis of current supply deals for COVID-19 vaccines, the ONE Campaign said wealthy countries, such as the United States and Britain, should share the excess doses to "supercharge" a fully global response to the pandemic. "If we are to end the global pandemic, life-saving innovations like vaccines must be within reach for all countries".
Canada has been getting all its Pfizer doses from a company facility in Puurs, Belgium, and has experienced disruptions in supply.
J&J said an emergency use listing is a prerequisite for supplying vaccines to the COVID-19 Vaccines Global Access Facility (COVAX) programme, co-led by World Health Organization, which aims to deliver doses to poor and middle-income countries.
COVAX hopes to provide vaccinations to at least 20% of the population in 92 of the world's poorest countries by the end of this year. The Biden administration is looking to develop a framework to donate excess vaccines "once there is a sufficient supply in the United States". The remaining $2 billion will be released over 2021 and 2022.
J&J entered into an agreement in December in support of the Covax programme.
The J&J vaccine is administered in a single dose and can be stored at normal fridge temperatures, a big selling point in countries with relatively weaker healthcare infrastructure.
The comments come one day before Biden will join the G7 virtual meeting, where leaders of major industrialized nations are set to address anxiety over a global vaccine rollout that's left behind poor countries.
Today's meeting will be the first hosted by the PM as part of the UK's G7 Presidency this year and the first gathering of G7 leaders since April 2020.
The other side: The White House said on Thursday's briefing call that the administration planned to turn to donations only after all USA demand was met.
Biden is also scheduled to deliver a virtual address to the Munich Security Conference on Friday before traveling to MI to visit Pfizer's vaccine manufacturing facility.