The head of the World Health Organization (WHO) has urged unity, as the agency comes under continued fire from US President Donald Trump.

Speaking on Wednesday, Director-General Tedros Adhanom Ghebreyesus defended the WHO's work and called for an end to the politicisation of Covid-19.

The Ethiopian also said that he had received deaths threats and has been subjected to racist abuse.

Mr Trump said he would consider ending US funding for the UN agency.

He accused the WHO of being "very China-centric" and said they "really blew" their pandemic response.

Dr Tedros has now dismissed the comments, insisting: "We are close to every nation, we are colour-blind."

After first attacking the WHO the previous day, President Trump renewed his criticism at his news briefing on Wednesday, saying the organisation must "get its priorities right". He said the US would conduct a study to decide whether it would continue paying contributions,

Also answering questions at the briefing on Wednesday, US Secretary of State Mike Pompeo said the administration was "re-evaluating our funding" of the WHO, adding; "Organisations have to work. They have to deliver the outcomes for which they were intended".

Covid-19 first emerged last December in the Chinese city of Wuhan, which has just ended an 11-week lockdown. An advisor to the WHO chief earlier said their close work with China had been "absolutely essential" in understanding the disease in its early stages.

Mr Trump's attacks on the WHO come in the context of criticism of his own administration's handling of the pandemic, especially early problems with testing.

The WHO approved a coronavirus test in January - but the US decided against using it, developing its own test instead. However, in February, when the testing kits were despatched, some of them didn't work properly and led to inconclusive results.

Public health experts say the delay enabled the virus to spread further within the US.

What did the WHO chief say?

"Please, unity at national level, no using Covid or political points," Dr Tedros said. "Second, honest solidarity at the global level. And honest leadership from the US and China.

"The most powerful should lead the way and please quarantine Covid politics," he appealed, in comments seen as a response to Mr Trump, who said on Tuesday the WHO appeared to be "very biased toward China".

The W.H.O. really blew it. For some reason, funded largely by the United States, yet very China centric. We will be giving that a good look. Fortunately I rejected their advice on keeping our borders open to China early on. Why did they give us such a faulty recommendation?

— Donald J. Trump (@realDonaldTrump) April 7, 2020

"They called it wrong. They really - they missed the call," Mr Trump said. "And we're going to put a hold on money spent to the WHO. We're going to put a very powerful hold on it, and we're going to see."

The US is one of the agency's largest voluntary funders, with WHO data suggesting they contribute 15% to its overall budget.

Dr Tedros said that he had been at the receiving end of racist comments for the past two to three months.

"Giving me names, black or negro," he said.

"I'm proud of being black, or proud of being negro."

He then said he had got death threats, adding - "I don't give a damn."

What has been the response?

Referring to the abuse, he said it had originated from Taiwan, "and the foreign ministry didn't disassociate" itself from it.

But Taiwan's President Tsai Ing-wen dismissed this, saying her country is against discrimination.

"For years, we have been excluded from international organisations, and we know better than anyone else what it feels like to be discriminated against and isolated," Reuters quoted her as saying.

Taiwan, which is excluded from the WHO because of China's objections to its membership, has said it has been unable to access important information during the coronavirus outbreak. The WHO denies this.

On Wednesday Dr Tedros played down the financial threat, saying he believed that US funding would continue.

United Nations Secretary-General António Guterres had earlier added his voice to the defence of the organisation. He described the outbreak as "unprecedented" and said any assessment of how it was handled should be an issue for the future.

"Now is the time for unity, for the international community to work together in solidarity to stop this virus and its shattering consequences," he said.

French President Emmanuel Macron also reportedly offered his support to the WHO in a call to Dr Tedros on Wednesday. "He reaffirmed his trust, his support for the institution and refuses to see it locked into a war between China and the USA," a French presidency official told Reuters news agency.

Timing of Trump's threat questioned

Facing growing criticism over his handling of this crisis, President Trump is now seeking to pin the blame for the spread of the coronavirus on the World Health Organization.

Officials at the UN agency criticised his decision to impose a ban on travellers entering the US from China at the end of January - a move the president has since touted as crucial to controlling the spread of the virus - and with conservative commentators and some Senate Republicans taking to the airwaves to denounce the Geneva-based body, Mr Trump has clearly decided it would be politically expedient to join them.

He sees the WHO as being biased towards China, and believes it was too unquestioning of the early information about Covid-19 that came from the Chinese.

The WHO is not above criticism, particularly for its early assertion that human transmission had not been proven and its reticence later on to declare a pandemic.

But even some of the president's leading supporters are questioning the timing of his threat to withhold funding for the world's leading health organisation - coming, as it does, at the height of a global pandemic.