Serena Williams on Monday called the alleged comments about her unborn child made by former world number one Ilie Nastase "racist" and applauded the International Tennis Federation for launching a probe into the remarks.

Former tennis bad boy Nastase, who won two grand slam titles in the 1970s, was quoted by Romanian and some British media as saying in response to William's pregnancy announcement: "Let's see what colour it has. Chocolate with milk?"

"It disappoints me to know we live in a society where people like Ilie Nastase can make such racist comments towards myself and unborn child, and sexist comments against my peers," the women's world number one wrote on her Instagram account.

"I am not afraid unlike you. You see, I am no coward. Does my sassiness upset you? Why are you beset with gloom? You may shoot me with your words ... you may try to kill me with your hatefulness, but still like air I will rise."

It would not be the first time Williams has been stung by racism as player.

The world number one boycotted the Indian Wells tournament for 14 years after she and sister Venus and her family claimed they were victims of racial taunts while Serena played in the 2001 final.

Nastase, 70, has been provisionally banned from all International Tennis Federation (ITF) events following his verbal abuse of British players last weekend in his role as Romanian Fed Cup captain.

Williams thanked the ITF and said they would have her full support as they investigated the matter.

"(The investigation) is ongoing. At this point, one of the principles that is important is that we want a rigorous process that is fair," ITF President David Haggerty said on Monday.

"We will also hear Nastase’s side of the argument. It will be a thorough process conducted in an efficient manner. I do not think you will be hearing any final decisions in the next two weeks."

British captain Anne Keothavong, who said she was made to feel "uncomfortable" by comments made by Nastase at the official pre-match dinner, said the abuse during play had been unacceptable.

"We expected a patriotic crowd for the Romanian team but we don't expect abusive language to be used ... what he said directed to both Johanna (Konta) and myself is ... language that is not appropriate for anyone to speak to any other human,” she said.

Konta was reduced to tears at one stage.