The World Health Organization (WHO) on Wednesday said it still needs one billion dollars to cover its 2026-27 budget as it scrambles to shore up its finances after the United States – the agency's top donor –severed ties in January.

US President Donald Trump's decision to halt its funding to the Geneva-based body upon returning to office forced it to scale back its originally approved budget by around 20 percent, from US$5.3 billion to US$4.2 billion, in May.

"This year has been one of the most difficult in WHO's history, as we navigated a difficult but necessary process of prioritisation and realignment, resulting in a significant reduction in our workforce," said WHO chief Tedros Adhanom Ghebreyesus during a Member State briefing.

"We are now nearing the end of this process," he said, confirming the UN health agency had secured 75 percent of the funding needed for the two-year budget.

"That's a better position than we have been in at this stage for any previous biennium."

However, he said the WHO still faced a US$1 billion shortfall, adding the agency was in "a much worse environment for mobilising resources than we have been in before".

In May, member states approved a 20 percent increase in mandatory contributions.

But the organisation still relies heavily on voluntary contributions from member states and other donors.

Faced with a decline in international aid, thousands of health facilities in humanitarian settings have had to cut services or suspend operations.

As a result, the organisation has had to prioritise those most in need of assistance in the toughest places.

The WHO chief said the implementation of various cost-saving measures had helped limit the number of positions the organisation had needed to cut.

While it had previously expected to be forced to shed around 2,900, Tedros said it had "managed to reduce the number of separations due to abolition of positions to 1,282".

In addition, he said 1,089 staff had left voluntarily, through retirement and early retirement, or as temporary contracts expired. (AFP)