The U.S. ambassador to Venezuela has grown used to facing protests and shouts of "Yankee go home!" But supporters of President Hugo Chavez appeared to cross the line when they pelted his car with eggs and tomatoes, then chased after his convoy on motorcycles.

The incident Friday drew a strong response from Washington, which summoned Venezuela's ambassador and warned him of "severe diplomatic consequence" in the event of a similar incident.

U.S. Embassy spokesman Brian Penn said Venezuelan police escorts did nothing to intervene as a car carrying Ambassador William Brownfield was pounded, kicked and pelted. No one was hurt.

"We were under attack by these motorcyclists throwing fruits and vegetables," Penn said. "They were pounding on the cars, including pounding on the ambassador's car while they were driving. There was no one stopping them."

It was the third time in three weeks that Brownfield has been met by protesters; other times, demonstrators have burned tires and torched an American flag.

Emotions have run high among Chavez supporters as the Venezuelan leader has accused the United States of plotting against him. American officials have denied it while accusing him of stifling democracy.

The latest protest began when Brownfield visited a baseball stadium in a poor Caracas neighborhood to hand out bats and other donated equipment for a youth league. He often holds public events to donate to charities and meet community leaders — even in Chavez strongholds.

This time, a Chavez supporter who described himself as an official of the Caracas mayor's office walked up and said people in the area wanted Brownfield to leave, Penn said. The ambassador stayed and finished the event, while a few dozen people outside chanted, "Go home! Go home!"

Penn said the barrage of tomatoes, eggs, onions and other items began when the convoy pulled out and drove through an adjacent market.

"Outside, the ladies and gentlemen who were protesting, stoning, egging, tomatoing, and then following, identified themselves — at least by their shouts and their screams — as members of the Tupamaros," Brownfield told Voice of America radio. "The Tupamaros is a clandestine organization, who describe themselves as urban guerrillas."

Leaders of the group, however, have renounced violence in recent years and formed a pro-Chavez political party.

The U.S. Embassy released a video taken from inside a convoy car, its windows splattered with broken eggs, showing motorcyclists racing up to the four-car convoy and then dropping back. At one point, Brownfield said, the car was stuck in traffic and the motorcyclists surrounded him, banging on the vehicle.

In Washington, State Department spokesman Sean McCormack said the incident "clearly was condoned by the local government." He said local officials were handing out snacks to the perpetrators at the stadium.

The mayor's office denied any involvement. Brownfield said the Venezuelan foreign ministry had called his office to express concern.

While at the stadium, protesters shouted: "Coup-plotter!" Some Venezuelans have accused Brownfield of conspiring with Chavez's opponents.

The ambassador denied it, saying his frequent public appearances are aimed at diplomacy and nothing more. "What I do in Venezuela is to try to project a positive image of the country and people I represent," he told reporters at the ballpark.

Everyone has a right to protest if they want, Brownfield said, but added, "I don't accept the right to violence."

He also made clear he wouldn't let the protests keep him from getting out in the community. "I don't accept the right of one group to tell me who I can meet with and who I can't," he said.