Of the many clashes in worldview between King Charles III and Donald Trump, the greatest is on an issue the White House has sought to silence: the future of the planet.

For more than 50 years, as Prince of Wales, the famously environmentally minded Charles spoke out frequently, addressing UN summits and closed gatherings alike to urge better guardianship of nature and strong action on the climate.

The royal visit to Washington will be no exception. The Guardian understands the king will not be silent on green issues, despite concerns within the government, and sources say the king is likely to touch on the environment in public as well as private. Civil society groups have been in touch with the palace over the potential inclusion of references to the climate and nature in the king’s speech to Congress on Tuesday afternoon.

Charles’s advocacy has never faced a more obdurate listener. Trump has all but declared war on the climate and nature, withdrawing the US from international climate agreements, halting progress on renewable energy and boosting coal, while opening drilling on public lands, cutting nature protection, bullying other countries who want climate action, sacking scientists and erasing mention of the climate from government communications.

There is little common ground between the UK and the US on the climate and environment, and the UK response has been to try to work around the problem in international forums, rather than force a showdown.

Charles is said to be skilled at broaching the subject in diplomatic ways, which he is likely to attempt with the US president and other prominent members of US government and business. “The king loves the natural world and understands that everything we have depends utterly on it,” said Ben Goldsmith, the investor, longtime environmental advocate and former chair of the Conservative Environment Network. “So I’d be amazed if he doesn’t raise the topic with president Trump.”

As well as expressing his own longstanding views, the king would be reflecting those of his nation, said Robbie MacPherson, Kennedy Scholar at Harvard University and former head of the UK parliament’s all-party group on climate. “People across the UK have chosen that a clean energy transition is their desired road to the future. The king should represent that view to foreign leaders including those who think that rolling back on environment and clean energy action is the correct course,” he said.

Will the president listen? Going by previous experience, it seems unlikely, according to Paul Bledsoe, a former Clinton White House climate adviser now with the American University. “Sadly, King Charles would be wasting his breath bringing up climate with Trump, but one hopes he features climate action prominently as an issue critical to public safety and global security.”

Goldsmith said that conservatives in the US had a “long and rich history of protecting America’s natural treasures”, and Trump’s political hero Teddy Roosevelt was father of the US national park system. “Today, the states doing most for wildlife are arguably Florida and Texas, both of which are securing large areas of land for rewilding and permanent protection. If Trump wants to Make America Beautiful Again, which is the name of one of his recent pronouncements, some focus on nature would seem an obvious move.”

MacPherson was also more hopeful, though for different reasons. “Across America, the clean energy transition and action to protect nature is happening,” he said. “A temporary shift in federal government delivery and blocking should not stop the long-lasting green special relationship shared between the UK and the US.”