Football's rule makers have approved changes in time for the World Cup, outlawing "unsporting" feints in penalty kicks and giving the fourth match official similar powers to assistant referees.

Players in South Africa who feint before kicking at the end of their run up to a penalty to trick the goalkeeper risk a yellow card for "unsporting behaviour", the International Football Association Board has decided.

They will also be forced to take the kick again if the ball goes into the net, FIFA Secretary General Jerome Valcke said after the IFAB meeting chaired by the president of world football's governing body Sepp Blatter.

The permanent rule change, which comes into force for the coming season, follows concern about the growing use of such feints in South America, where players paused to see which way the goalkeeper was diving, officials added.

The amended rule says: "Feinting in the run-up to take a penalty kick to confuse opponents is permitted, however feinting to kick the ball once the player has completed his run-up is now considered an infringement... and an act of unsporting behaviour for which the player must be cautioned."

Meanwhile the fourth match official, who normally oversees substitutions, off pitch behaviour and match management gained expanded powers allowing him to "assist the referee to control the match" in on-pitch incidents, according to the amended rule.

"Today he's as important as the other officials on the field," Valcke told journalists.

The rule change nonetheless keeps the supreme powers of the referee "to decide on all points connected with play."

The IFAB also agreed on Tuesday to extend a European experiment of using four assistant referees on the pitch worldwide, allowing football leagues and regional confederations to try it out over the next two seasons.

The trial, FIFA added, was not compulsory.

"What is clear is that we're not changing the rules of the game before the end of the trial," said Nelson.

Blatter and the IFAB have ruled out the introduction of electronic aids such as video replays and goal mouth cameras to help referees spot match incidents in the ever faster modern game.

European governing body UEFA has experimented with two extra assistant referees in some 200 Europa League matches over the past two years as an alternative.

While IFAB members said they had received a report on the UEFA experiment containing "positive" elements, some of them were skeptical about the idea although they supported more trials.

Valcke insisted that future trials must be carried out over a full season to amass enough match experience.

"If the FA Premier League decides to go for a trial, they have to carry it out from beginning to end of the season," he said.

Countries aiming to hold trials must seek authorisation from an IFAB sub committee at the end of July.

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