The United States and Germany on Thursday urged greater efforts to combat the denial and diminishing of the Holocaust, warning against complacency as conspiracy theories thrive online and survivors pass away.

The top diplomats of the two allies announced a new initiative involving policymakers and Holocaust museums that will look for more "innovative" ways to teach about the genocide that killed six million Jews as well as Roma, LGBTQ people and other minorities.

US Secretary of State Antony Blinken, the stepson of a survivor of the Auschwitz and Dachau death camps, said the Holocaust was a "gradual descent into darkness" made possible by "countless individual steps designed to vilify and dehumanise people".

"That understanding is particularly urgent today as survivors pass from us and those who deny the Holocaust are getting louder and finding insidious new ways to spread their lies," Blinken said in Berlin at the Memorial to the Murdered Jews of Europe, pointing to a sharp rise in anti-Semitic content online.

Blinken was visibly moved as he heard from 99-year-old Margot Friedlaender, a camp survivor who still speaks several times a week of her experiences, including how her murdered mother left her with a necklace and the message, "Try to make your life."

"You've done a remarkable thing with your first 100 years. We'll wait for the next 100 years to see what you do next," Blinken was heard saying as he squatted by her seat to chat with her under light rain.

German Foreign Minister Heiko Maas voiced outrage at protesters against Covid vaccines and mask-wearing who have donned the yellow Stars of David forced on Jews by Nazi Germany and he linked the rise of conspiracy theories to the January 6 mob attack on the US Capitol.

"The strength of America, Germany and Europe does not come from glorifying history or glossing over the mistakes of the past," Maas said.

"Our strength lies in shouldering the burden of historical responsibility, without any ifs or buts. Our strength lies in joining forces in search of the best way forward."