Trump honored three Native Americans, all in their 90s, who helped the US Marine Corps develop a secret code using the Navajo language during the Second World War.

“I just to say thank you because you’re very, very special people. You were here long before any of us were here,” Trump said. “Although we have a representative in Congress who, they say, was here a long time ago. They call her Pocahontas.”

Turning to the veterans, Trump added, “But, do you know what? I like you."

The president’s critics took this as a reference to Senator Elizabeth Warren (D-Massachusetts), who controversially claimed Native American heritage in her earlier career as a college professor.

During the event, Trump also referred to White House chief of staff John Kelly as “Chief,” and stood under the portrait of President Andrew Jackson, who signed the Indian Removal Act in 1830, ordering the forcible relocation of Native tribes to present-day Oklahoma. The Navajo lands are in present-day Arizona and New Mexico.

The Twittersphere was not amused.

Trump's nickname for Warren "smacks of racism," John Norwood, general secretary of the Alliance of Colonial Era Tribes, told NBC News. “The reference is using a historic American Indian figure as a derogatory insult and that’s insulting to all American Indians.”

Norwood added that the president should “stop using our historical people of significance as a racial slur against one of his opponents.”

White House press secretary Sarah Huckabee Sanders took issue with reporters who characterized the remark as a racial slur during the daily press briefing on Monday afternoon.

“I think what most people find offensive is Senator Warren lying about her heritage to advance her career," Sanders told reporters.