FIFA has blocked more than 100 requests to transfer young players across national borders as it seeks to curb what it refers to as ''trafficking.''

FIFA official Mark Goddard said Thursday that more than 10 percent - 118 of around 1,000 applications to trade under-18 players - have been rejected since a tougher transfer monitoring system was introduced last October.

''Early signs are that it's certainly much harder'' to transfer youngsters, Goddard told reporters in a conference call. ''We're starting to see behavior change.''

FIFA blocked some proposed deals because of fraudulent documents.

''It's certainly a factor. There's a lot (of cases),'' said Goddard, who manages FIFA's Transfer Matching System, an online database of international trades.

FIFA lawyers are weighing disciplinary action against national associations, clubs or agents in ''tens'' of attempted transfer cases.

Goddard acknowledged that trafficking has not been stopped yet, and that some clubs and agents are still finding ways to cheat the system.

''We don't necessarily think all minors are going through the system, but we're working on ways to make sure that becomes a very bad decision,'' he said.

FIFA passed rules in 2009 restricting youth transfers because too many schoolboys were being lured abroad with the promise of a lucrative professional contract that often never materialized.

''It got to a point where it was getting too extreme,'' Goddard said.

Some deals are still allowed after vetting by a panel from FIFA players' status committee, which can decide if players are moving to pursue their education or because a parent has a new job. Players aged 16 or 17 can also move freely between European Union members.

FIFA monitoring was strengthened when a system to match transfer documents became mandatory last year for cross-border deals involving players of all ages.

The system seeks to stop financial corruption and identity fraud by requiring both clubs in a trade to input more information online. FIFA can block deals when details don't correspond.

Goddard said feedback from FIFA members in South America suggested that trading minors was now simply too much work, and clubs preferred waiting until a player was 18.

However, FIFA understood that clubs are naturally competitive and will seek to get an edge.

''One of the ways seems to be going younger and younger - you get them earlier, you get them cheaper,'' Goddard said.