Nelspruit, South Africa: The deafening noise of South African football's plastic trumpet, the vuvuzela, has the potential to be a weapon for the country's World Cup campaign, former England captain Bryan Robson said on Sunday.

Robson's Thailand team lost 4-0 to South Africa in a warm-up international on Sunday, played in front of a near capacity crowd of 42,000 at the new stadium in Nelspruit to a soundtrack of ear-splitting and tuneless trumpeting that drowned out any instructions from the bench.

"I think with that noise South Africa could have an advantage in the World Cup," Robson told reporters, explaining he could not get any instructions to his players above the constant cacophony.

"If the atmosphere is like that in the World Cup it will raise the level of the players a little bit. If the supporters are behind them like that, it will be a big boost," he said.

Difficult

Complaints about the vuvuzela during last year's Confederations Cup in South Africa were rejected by Fifa, who said there would be no ban on the long plastic instrument at the World Cup.

"The coaches at the World Cup are definitely going to have to inform their players beforehand that they will have to communicate effectively with each other on the field," added the former Manchester United player.

"It's very difficult to get any message to the players from the bench. Coaches are going to have to make that known to their players."

Robson had to call players over to the side of the pitch on several occasions during Sunday's international to try and pass on instructions.

"We have to reinforce that advantage," said South Africa's coach Carlos Alberto Parreira in response. "We want it louder and louder."

The World Cup in South Africa runs from June 11 to July 11.