America's special envoy on climate change John Kerry has told Sky News that it would be "very powerful" if King Charles could attend the COP27 UN climate summit in Egypt.
Mr Kerry's comments come as Prime Minister Rishi Sunak announced that he would not be going.
Earlier this month it was reported that Liz Truss had asked the new monarch, who is famously passionate about environmental issues, not to go despite being invited.
In an interview, Mr Kerry said: "I think it would be terrific, personally.
"I know that his being there would make a difference… because he has credibility because he's been a long-term leader.
"I think it would be very powerful."
The UN has warned that the world is on course for catastrophic temperature rises if more isn't done.
Mr Kerry said the situation was worrying, adding: "Right now, (nearly) every government in the world is off course… every one of the 20 largest economies of the world that represent 80% of all the emissions are off target at this moment.
"Can they get on target?
"If they fully implement plans they've made, or for a bunch of them, if they step up in Sharm El-Sheikh and raise their ambition as the Glasgow agreement calls on all nations to do."
On Wednesday, it was reported that combined US experts of crude oil and refined petroleum products surged to 11.4 million barrels a day the previous week - the highest level ever reported.
When asked if this has compromised the country's credibility on climate change, Mr Kerry pointed to the global energy crisis, saying: "We're trying to stop-gap.
"Those are countries that have fuel needs as a consequence of what Russia has done by invading Ukraine.
"So clearly, that disrupted the supply for them of fuel to keep their economy moving and keep their homes heated and the lights on.
"None of us are suggesting that you crash economies around the world. We don't have to do that. We can have an orderly and sensible process of transition. That's what we're trying to affect."
The International Energy Agency says the energy crisis could end up accelerating the green revolution.
But on Thursday, Shell announced another near-record profit as a result of high oil and gas prices.
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The UN Secretary-General Antonio Guterres has called for fossil fuel companies all over the world to make payments to those most damaged by the climate crisis.
When asked if America had engaged with that idea, Mr Kerry said: "President Biden feels very strongly that we need to have fairness in this transition.
"There has to be just transition and it's important for us to try to find a way to reflect what's happening with the price of carbon, and to be fair to citizens around the world who've had pressure put on them.
"I think the US is open to ideas that are going to allow justice in the transition so that the average citizens of countries are not getting unfairly squeezed.
"The American position is that they're going to take a look at everything that's being put on the table and it will be part of a conversation about justice and fairness."
Defining issue at COP27
Who foots the bill for the damage inflicted by climate change will be a defining issue at COP27.
For many nations, the costs are already running into the tens of billions and without help, they say they simply cannot pay.
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