Eric Trump, son of US President Donald Trump, has said he was spat on by an employee at an upscale Chicago cocktail bar.
"It was a purely disgusting act by somebody who clearly has emotional problems," Mr Trump said to Breitbart, a right-wing news website.The employee was questioned by Secret Service agents and later released, according to local media.
The bar confirmed that an "unfortunate incident" had occurred with Mr Trump.
"We did not witness the incident and we are just beginning to learn the details," the Aviary said in a statement. "What is certain is this: no customer should ever be spit on."
Mr Trump told Breitbart that he declined to press charges against the employee, who has been placed on leave by the bar.
A spokesman for the Chicago police confirmed on Twitter that local officers assisted the Secret Service on Tuesday evening with a "law enforcement matter" but did not elaborate further.
The incident occurred at the Aviary, a James Beard Award-winning cocktail bar in Chicago's West Loop neighbourhood.According to local media, Mr Trump was at the bar at around 20:30 local time (01:30 GMT) on Tuesday when he was spat on by an employee.
The Aviary's co-owner, Nick Kokonas, made headlines in January this year when he invited the Clemson Tigers, national college football champions, to "an actual celebration dinner" at his restaurant, Alinea, after the president served the players fast food at the White House.
President Trump, who hosted the team during the longest ever US government shutdown, paid personally for the meals.
Mr Trump, executive vice president of the Trump Organisation, was in town on a visit to Chicago's Trump Hotel.
He told Brietbart he believed the incident was politically motivated.
"For a party that preaches tolerance, this once again demonstrates they have very little civility," the president's third child said, apparently suggesting the employee was a Democrat.
"It just emphasizes a sickness and desperation and the fact that we're winning."
The alleged spitting is part of a series of incidents in which members of the Trump team have been harassed or confronted over policy differences while dining out.
Last June, activists heckled then Homeland Security Secretary Kristjen Neilsen at a Mexican restaurant in Washington DC. Days later, former White House press secretary Sarah Sanders was asked to leave a restaurant in Lexington, Virginia because she worked for the Trump administration.