Two weeks after it was announced Formula One was leaving the United States, the lone American in the series is now gone.

SPEEDtv.com has learned that Scott Speed will be replaced -- immediately -- on the Scuderia Toro Rosso Formula One team following a stormy weekend at the Nurburgring.

A source inside the Red Bull-sponsored team confirmed that Speed got his walking papers Monday after a physical confrontation with team manager Franz Tost. German Sebastian Vettel is the likely choice to replace the young American.

"As far as I know, Scott has not been released and he's planning to go to the test this week in Italy," said Mike Speed, father of the former go-kart star, from his California home on Monday night.

"But, obviously, there's been a lot of things going on."

After spinning out of last Sunday's German Grand Prix, along with six other drivers during a sudden downpour at the 'Ring, Speed and Tost got into a shouting, then shoving match.

And this came on the heels of the 24-year-old's first public statements about his treatment since becoming a full-time F1 regular in 2006.

“It’s clear that from my bosses, that me and Tonio (Liuzzi) both have very little support," Speed told RACER magazine's Adam Cooper last weekend. "It’s been that way for the last two years, and it’s a lot more now. At some point I said I don’t care, if I’m not in F1 next year, if I’m with a different team, it’s OK for me. It’s actually made me lot more relaxed and a lot more calm, and I think I’m producing better results now actually.

"It doesn’t take a rocket scientist to read the press and know that Franz and Gerhard (Berger) are pushing like hell to get rid of me and Tonio."

Even though Speed has out-performed his teammate this year, neither has scored a point and Scott's best showing was ninth at the Canadian Grand Prix. The Toro Rosso team is under-funded, by F1 standards, and half of Speed's eight DNFs in 2007 have been mechanical failures.

SPEEDtv.com speculated several weeks ago that three-time Champ Car king Sebastien Bourdais and Bruno Senna would replace Speed and Liuzzi in 2008 but, if Vettel is released from his contract with BMW, it appears he will join Bourdais.

"Nothing is official, they (Toro Rosso) have an option on me that expires at the end of this month so if something is going to happen it will have to be soon," said Bourdais, who tested for the third time with Toro Rosso earlier this month.

Speed was first chosen by the energy drinks company as part of its U.S.-based Red Bull Driver Search program, which funded the Californian's climb through Europe's junior formulae ranks all the way to F1. It's logical he might be able to use that connection to come to Champ Car since that series needs young American drivers. Co-owners Gerald Forsythe and Kevin Kalkhoven currently sport Red Bull sponsorship.

"We haven't discussed anything like that," said Mike Speed. "Scott never wanted to do anything but F1 and I don't think that's changed."

It may be an exercise in futility now that America has lost its sole Formula 1 driver, but Toro Rosso team principal Franz Tost added more fuel to the fire of the controversy of his altercation with Scott Speed by denying to have grabbed the Californian by the neck – something he was accused of doing by the driver – during their argument at the European Grand Prix.

“There were a couple of people who saw. He grabbed me right below the neck, on my fireproof T-shirt, and jerked me back and forth, let go, and then pushed me into the wall behind where the cars are,” Speed told SpeedTV.com’s Adam Cooper last week.

Tost says he did not grab Speed by the neck, adding that the incident was provoked when Speed was very critical of the team after his pit stop was delayed following torrential rain at the Nurburgring. Speed retired from the race after spinning out when the downpour hit the track.

"When Scott came to the pit wall after going off the track, he complained about the very bad performance of the team because of the delay he suffered during the pit stop," Tost told Italy’s Autosprint.

"By contrast, I firstly asked him why he went off, then I tried to explain to him that he was the one who actually caused the chaos, but he didn't listen to me. He carried on wanting to know why the team took so long to change his tires when he came into the pits. It seemed like that was his only worry, while mine is, most of all, that the team are not put in doubt and their job not denigrated.

"There was a reason why the pit stop lasted that long: in his in lap Scott overtook our other car - that of Vitantonio Liuzzi - in the last sector. The GPS fit on our cars did not show that Scott had overtaken Tonio, cutting through the chicane, just before entering the pitlane. [The GPS] maybe didn't have enough time to catch the move. The team there, who were expecting to see Tonio coming, were left dumbfounded and were unprepared. Scott overtook his teammate by avoiding the chicane and I think he would have had to give back the position to avoid a penalty, if he stayed in the race.

"That's why I got upset: I was annoyed by his attitude, by the fact that his only worry seemed to blame the team. I mean, he went off the track, he made a mistake: I make mistakes every day as well, that's not the problem. But I can't tolerate that he casts a cloud over the work of the team.

"That's why, when he turned around to leave, I followed him and grabbed him by the shoulder. 'While I'm talking to you,' I said, 'you can't leave like this.' I deny having grabbed him by the neck, while it's true that, once I had calmed down, I apologized to him."

Yesterday it was confirmed that Speed has been given his walking papers by the team. German rookie Sebastien Vettel will replace him alongside Tonio Liuzzi.