Sir Elton John said he is ready to 'fight' and go 'face to face' with President Trump over cuts to AIDS relief spending.
Global health funding by the United States to address the global HIV/AIDS epidemic has been under threat since the Trump administration came to power.
The Rocketman singer, 78, refused to criticise Trump's White House because of his work with the Elton John Aids Foundation, but he did say that the political landscape looks 'a little shaky'.
As a decades-long AIDS campaigner, Sir Elton acknowledged that he had to be 'a diplomat'.
Speaking at the London Palladium on Wednesday night, he said: 'I cannot speak out about governments. I'm a diplomat.
'If I speak out about governments, then what's going to happen to the AIDS money? What's going to happen to PEPFAR [The U.S. President's Emergency Plan for AIDS Relief]?'
Sir Elton John has said he is ready to 'fight' and go 'face to face' with President Trump over cuts to AIDS relief spending
'I've got people's lives at stake. I have an AIDS foundation that depends on money, and I will go there and fight for it as much as I can.'
'But I cannot go out and say, ''You're an a**hole. You're an a**hole.'' That's not what it's about. You have to negotiate. You have to play the game.'
The Candle in the Wind singer then praised past US presidents for the action they have taken to combat the AIDS crisis, and indicated his willingness to fight against any moves to change that.
Sir Elton said: 'To be fair to all the governments, since George W Bush, who initiated Pepfar, to Donald Trump, they have kept Pepfar going.'
'It looks a little shaky now. But I'm going to go there and fight for it, even if I have to go face to face I will.'
It raises the prospect of Sir Elton campaigning in Washington DC, reminiscent of the late actress Elizabeth Taylor's crusading in the American capital.
Taylor was a prominent AIDS activist, who, after the death of her friend Rock Hudson from AIDS, became a vocal advocate for research and funding.
The Cleopatra actress lobbied President Reagan at the White House, and testified before Congress to ensure Senate support for the Ryan White CARE Act of 1990, which remains the primary source of federal funding for HIV/AIDS programs nationwide.
Global health funding by the United States to address the HIV/AIDS epidemic has been under threat since the Trump administration came to power (President pictured on Wednesday)
As a decades-long Aids campaigner, Sir Elton, speaking at his show at the London Palladium, acknowledged that he had to be 'a diplomat'
Sir Elton has also been a long-time AIDS campaigner and was instrumental in lobbying to set up the two-decade-old President's Emergency Plan for Aids Relief, which was launched by President George W Bush in 2003 and is estimated to have saved over 25 million lives globally.
Pepfar was made exempt from the cancellation of most US overseas aid, after the Trump administration initially put the program on halt and took its computer systems offline.
But the Pepfar is still heavily reliant on logistical support from the US Agency for International Development (USAid) and the UN has warned it will have a devastating impact.
Christian evangelical groups have also urged the President to spare the HIV/AIDS program from the crushing cuts.
Emily Chambers Sharpe, health director at World Relief, the humanitarian arm of the National Association of Evangelicals, said that healthcare centers and hospitals in Africa have reported 'the supply chain for HIV as a whole has been very badly damaged' by the aid cuts.
Matthew Loftus, a doctor and evangelical Christian working at a mission hospital in Kenya, told The Guardian that the damage was already being done on the ground. He said that Pepfar 'is being dismantled' and that 'many people will die' as a result.
'In some places they're not getting the drugs or they're being asked to pay cash for the drugs. Other places are completely closed and so patients are scrambling to find medications or they're going without,' he said.
He added: 'There are going to be consequences. Once you stop taking ARVs, within days the virus can come back online and then start developing resistance.
'I'm really scared that there are going to be a bunch of people who haven't been taking their drugs and then, when we try to start them back, we're going to find that they're resistant.
'They could turn everything back on tomorrow and I think there would be permanent damage. Once you fire people and close clinics, rebuilding trust is difficult, getting people to come back is difficult.'
It is estimated that about 20 million people are reliant on medicines supplied by Pepfar mostly in Africa and parts of Asia.
Countries like Nigeria depend on Pepfar for almost all their HIV funding. Others are less dependent on the program, but Pepfar still provides important health infrastructure because its clinics employ medical staff who treat other conditions as part of the broader programme of combatting Aids.