In a statement released on Friday, WTA chief executive Stacey Allaster blasted the remarks made on a late-night chat show, which according to translations circulated on English-language social media included referring to the US superstars as the "Williams brothers."

"The statements made by Shamil Tarpischev on Russian television with respect to two of the greatest athletes in the history of women's tennis are insulting, demeaning and have absolutely no place in our sport," Allaster said.

Officials of the worldwide women's tennis tour said that the USD 25,000 fine is the maximum allowed under their rules.

They are also banning Tarpischev for one year from involvement with the tour and are seeking his removal as chairman of the Kremlin Cup tournament for a year.

The 2014 edition of the combined men's and women's tournament in Moscow is underway this week.

"The WTA was founded on the principles of equality, opportunity and respect, and Venus and Serena embody all of these attributes," Allaster said.

"Mr. Tarpischev's statements questioning their genders tarnish our great game and two of our champions. His derogatory remarks deserve to be condemned and he will be sanctioned."

Allaster said she had received a private letter of acknowledgement from Tarpischev that she called "a start."

However, she added that he owed the Williams sisters an apology.

US Tennis Association Chairman and president Dave Haggerty also called on Tarpischev to apologize.

"As the president of the USTA and a member of the Board of Directors of the International Tennis Federation, I call on Shamil Tarpischev to issue a formal apology to Venus and Serena Williams," Haggerty said in a statement.

"As the president of the Russian Tennis Federation and a member of the International Olympic Committee, Mr. Tarpischev is expected to conduct himself with the highest degree of integrity and sportsmanship."

World number one Serena Williams won her 18th Grand Slam singles title at the US Open in September.

Elder sister Venus has won seven Grand Slam singles titles.

Latest News from Sports News Desk