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Williams boss Patrick Head has heavily criticised his drivers Juan Pablo Montoya and Ralf Schumacher for crashing into each other at the US Grand Prix.

The two men collided while disputing fourth place at the start of the second lap.

The clash left Schumacher with no rear wing and dropped Montoya to seventh place.

Head said: "I'm not into apportioning blame between the two of them.

"We've had some fantastic drivers in the past but they just haven't driven into each other. It's absolutely ridiculous.

"For the amount of effort that goes into this, to have that happen is completely unacceptable. We'll talk about it afterwards and try to sort out how it doesn't happen again."

The crash probably prevented Williams securing a third place in the race.

Montoya was closing rapidly on McLaren driver David Coulthard in the closing laps but ran out of time to catch him.

Head, the team's technical director, also criticised Montoya for making his pit stop at the wrong time.

"We did everything to try and not get a podium," Head said.

"He came into the pits for his pit stop when he had lots of fuel on board for many more laps, so why he came in we don't know. We'll have to look at it afterwards.

"Altogether we found the ways of doing it wrong. We should have had a good solid third and fourth here."

Montoya was trying to pass Schumacher having dropped behind him at the start.

The two drivers went into the first corner side by side with Schumacher on the inside.

But the German spun and hit Montoya's car, knocking off his own rear wing and pushing the Colombian wide.

Montoya said: "He made a mistake. I went around the outside to pass him and braked really late and I think he spun.

"He pushed me off the track and that was about it."

Schumacher said: I had a good start but there was an unlucky event with Juan.

"It is always very difficult to overtake someone on the outside. There wasn't enough room.

"I'm going to have to watch the TV to get a clear picture of what happened," he added.

It is the second time in two races that the two men have tripped over each other.

In Italy two weeks ago, Schumacher cut the first chicane while passing Montoya at the start and was ordered by race officials to let the Colombian past him again.