* Spanish league takes legal action to halt suspension
* Dispute centres on changes to sale of TV rights
* Current system favours big clubs Real and Barca (Adds LFP legal action against AFE)
MADRID, May 7 (Reuters) - Spain's professional league (LFP) has taken legal steps to overturn a decision by the soccer federation (RFEF) to suspend matches from May 16 over a dispute with the government on a new TV rights law.
The federation's pledge on Wednesday to halt matches, which was backed on Thursday by the players' union (AFE), threatens to throw the final weeks of the La Liga season into chaos and sideline some of the world's top stars, including Real Madrid's Cristiano Ronaldo and Lionel Messi of rivals Barcelona.
The decisive last two matchdays in La Liga could both be hit as well as the King's Cup final between Barca and Athletic Bilbao because of a clash over how TV rights are sold.
New regulations would replace the current system under which rights are marketed by individual clubs -- unique among Europe's top leagues where collective bargaining is used -- and could lead to a sharp price increase in costs for broadcasters once it takes effect from the 2016-17 season.
The status quo heavily favours Real, the world's wealthiest club by income, and Barca. The new set-up would still be weighted towards the biggest clubs but to a lesser extent.
LFP president Javier Tebas, whose relationship with his RFEF counterpart Angel Maria Villar has broken down, said the suspension would harm the image of Spanish soccer.
"The damage would be terrible and widespread," Tebas told reporters in Madrid.
"Even from China they have expressed concern about the consequences this could have for our sponsors," he added.
"If the government submits to this blackmail we would be taking a step backwards in the regeneration of Spanish soccer."
The TV rights legislation was signed off in cabinet last week after months of delays and aims to create a more level playing field for clubs in Spain's top two divisions by sharing out cash more equitably.
Poorer teams, especially those with big outstanding tax bills, have for years called for rights to be pooled to help them make ends meet.
However, both the RFEF and the AFE have come out against it and the two groups have backed halting competition across all Spanish soccer.
Barca captains Xavi and Andres Iniesta and Real captains Iker Casillas and Sergio Ramos were among players who attended an AFE news conference in Madrid on Thursday at which the union complained the TV law does not protect their rights.
The LFP responded to the AFE's decision to side with the RFEF by saying it would file a petition with a Spanish court on Friday to block the move.
The RFEF accuses the government of a "lack of respect" and complains it has not been consulted properly.
It believes the law will rob it of some powers and is unhappy at what it says are plans to use of money from soccer to fund other sports.
The LFP said the RFEF's decision was legally "invalid" and that it had initiated "the appropriate action with the pertinent administrative and legal bodies" to overturn it.
Spanish law gave the LFP the right to organise professional competition and set the calendar for matches, the league argued, and called for those involved in voting for a suspension to be subjected to disciplinary measures. (Reporting by Iain Rogers; Editing by John O'Brien and Keith Weir)