The ITF, which already co-ordinates the testing for the ATP men's tour, will assume responsibility for overseeing the testing procedures for the WTA women's events.

Beginning in January, the ITF will enforce penalties and manage and administer the testing for all tournaments sanctioned by the WTA, said ITF president Francesco Ricci Bitti.

"It will strengthen and enhance the anti-doping in our sport," said Ricci Bitti. "We have to be vigilant with anti-doping in our sport. It is the best way to cope with the problems all sports have."

Speaking at the start of the second week of the US Open, Ricci Bitti said the ITF is expanding on the testing currently done at Grand Slam tournaments and Fed Cup events.

But the biggest change the women's players will see is a significant increase in of-out-of-competition testing.

"Last year almost every one of our top 20 players were tested out of competition. This agreement will enable us to do more," WTA chief executive Larry Scott said of the project which will cost about 1.5 million US dollars annually.

He said the ITF plans to administer between 1,500 and 2,000 total tests next year. In 2002, the ATP conducted 919 in-competition and 71 out-of-competition tests.

Ricci Bitti the project will cost about 1.5 million US dollars annually.

Tennis does not appear to have as big a problem with doping as track and field, cycling or American baseball but there have been cases of drug cheats getting caught.

Earlier this year, Bulgarian tennis star Sesil Karatancheva was slapped with a two-year ban after testing positive for the steroid nandrolone at the 2005 French Open.

Russian Svetlana Kuznetsova was the subject of doping speculation in 2005 when she was named by a Belgian sports minister as a player who tested positive for the banned substance ephedrine during an exhibition match in Belgium.

World number seven Kuznetsova, who plays a fourth round match Sunday against 19th seeded Jelena Jankovic, blamed the positive result on medication she was taking for a cold.

Four years ago, Spain's Lourdes Dominguez Lino was suspended three months from the WTA Tour after testing positive for cocaine. Lino, who is ranked 41st in the world, lost her opening match at the US Open 6-1, 6-2, to American Serena Williams.

Her countryman Rafael Nadal said last week before the start of the US Open that he had been tested 17 times in the past year. Nadal's name was falsely linked by a French Sunday newspaper to a Spanish cycling doping scandal.

The newspaper reported last month that Nadal's name was on a list which also included five players from the Real Madrid football team. Nadal has vehemently denied the accusations.

"It is not true," Nadal said last week before the start of the US Open where he is seeded second. "Everybody knows it is not true. I have 17 anti-doping controls every year so that's stupid to say. It is nothing."

The Spanish government issued a statement clearing Nadal of any wrongdoing.

The reigning French Open champion Nadal is having the best US Open of his career. The 20-year-old Spaniard faces Czech Jiri Novak in a fourth-round US Open encounter on Monday for a berth in the quarterfinals.