GENEVA- A U.S. official told a World Health Organization meeting on Tuesday that Washington would participate in a programme to boost COVID-19 testing, diagnostics and vaccines as it joins global efforts to respond to the pandemic.

WHO chief Tedros Adhanom Ghebreyesus welcomed the announcement which follows confirmation last month that Washington under President Joe Biden will remain in the Geneva-based agency. Former President Donald Trump criticized the agency and halted funding.

"We want to underscore the commitment of the United States to multilateralism and our common cause to respond to this pandemic and improve global public health," Colin L. McIff, Acting Director at the Office of Global Affairs in the U.S. Department of Health and Human Services, said at a WHO virtual meeting.

The meeting in Geneva aims to help fill a $27 billion funding gap for the WHO-backed programme, called the Access to COVID-19 Tools (ACT) Accelerator Facilitation Council, that is aimed at broadening global access to COVID-19 fighting tools.

The United States had previously been an observer to ACT.

The United States, the top donor to the WHO, has pledged $4 billion. WHO's Special Envoy for the ACT Accelerator Andrew Witty, a former GlaxoSmithKline CEO, said discussions on further support from the United States were ongoing.

In the same meeting Tedros expressed fresh concerns about vaccine inequity, noting that 90% of countries rolling out COVID-19 vaccines are wealthy and that 75% of doses have been deployed to just 10 countries.

South African Health Minister Zweli Mkhize who co-chairs the meeting called these "alarming and disappointing numbers which we need to change".

(Reporting by John Miller, Michael Shields and Emma Farge) ((emma.farge@thomsonreuters.com;))