The head of the world's largest scientific membership organisation has given his backing for a planned protest by researchers in Washington DC.
Rush Holt, of the American Association for the Advancement of Science (AAAS), said that people were "standing up for science".
His remarks reflect growing concern among researchers that science is disregarded by President Trump
Scientists across the US plan to march in DC on 22 April.
"I've never seen anything like it in my entire career," the former Democratic congressman told BBC News.
"To see young scientists, older scientists, the general public speaking up for the idea of science. We are going to work with our members and affiliated organisations to see that this march for science is a success."
Mr Holt made his comments at the AAAS annual meeting in Boston as President Trump appointed a fierce critic of the Environmental Protection Agency as its head. Scott Pruitt has spent years fighting the role and reach of the EPA.
Campaigners accuse him of being too close to the oil and gas industry, and allege that he is "lukewarm" on the threat posed by climate change.
Rush Holt says that the concern among US scientists has gone well beyond the usual uncertainty that comes with a change in the Oval Office.
"It is partly because of the previous statements of the president and his appointees on issues such as climate change and vaccination for children which have not been in keeping with good science," the AAAS CEO told BBC News.
"But mostly by what we have seen since the new administration has come in, [which] is silence about science. Very few appointments to positions are filled by people who understand science, very few comments about the importance of science; there is no science advisor in the White House now and we don't know whether there will be one.
"And so the silence is beginning to sound ominous."
There has been unease among researchers ever since Mr Trump was elected in November. More than 600 professors from one of the country's leading research Universities, MIT, signed an open letter before his inauguration expressing their concerns.
It stated: "The president-elect has appointed individuals to positions of power who have endorsed racism, misogyny and religious bigotry, and denied the widespread scientific consensus on climate change... Science is not a special interest; it is not optional. Science is a foundational ingredient in how we as a society analyse, understand, and solve the most difficult challenges that we face."
Among the signatories' worries are the president's statement that climate change is a hoax, his alleged muzzling of environmental agencies and his apparent interest in setting up a commission to investigate whether vaccines cause autism.
Prof Nancy Kanwisher, who is a brain researcher at MIT, explained why she helped organise the petition.
"This is the most frightening and serious threat we have faced in my lifetime," she told BBC News.
"The political tactic of denying scientific fact is a huge threat to the health of our people. It is also a huge threat to our planet from climate deniers."
Sarah Schwettmann, who is a PhD student working with Prof Kanwisher, said that many of her fellow students felt just as strongly as their professors.
"Science has unfortunately taken a political beating," she argued. "It has been drawn into a realm where we have to stand up for the necessity of science in informing public policy and potentially averting the global crisis we see in environmental change and climate change."
Ms Schwettmann has designed black-hooded sweatshirts for protestors. On the back is "MIT" in the shape of a clenched fist. On the sleeves is the electrical symbol of resistance.
But President Trumps supporters, such as Myron Ebell, who is a director at a libertarian advocacy group, Competitive Enterprise Institute, accuses the academics of being an out-of-touch elite - and says they should listen to the electorate.
"The people in the heartland of America who make stuff, dig up stuff and grow stuff for a living voted for Donald J Trump as president," he told BBC News.
"The people living in New York City and working in the university towns across America did not vote for him. They lost the election and they are going to have to get used to it."
There is little sign of that happening. All across the country many scientists are preparing for their march for science on Washington. They are in a battle to win the hearts and minds of their countrymen.