Romanian tennis great Ilie Nastase apologised for derogatory comments about former world number one Serena Williams, who is pregnant, and for a foul-mouthed Fed Cup tirade that saw him suspended by the International Tennis Federation (ITF).

Nastase was overheard last Friday by a journalist talking about Williams' unborn baby being "chocolate with milk".

Williams is black and her fiance, Alexis Ohanian, is white.

Nastase said the comment was a "spontaneous" reaction to hearing Williams was expecting her first child.

"My words during the Fed Cup have rightfully caused controversy and upset the audience, the press and, most painfully for me, the tennis world," the former world number one, 70, said on Facebook.

"I am fully aware that nothing can truly excuse my statements - not the tension of a high-stakes game, not my traditionally irreverent attitude, not the unfortunate escalation of the situation.

"My life remains dedicated to tennis and its audiences, so please accept my apologies, for whatever they may be worth right now."

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Nastase also said Williams was "one of the greatest players of all times and I know how much work goes into achieving these results".

The comments last Friday prompted outrage from Williams, the 23-time Grand Slam winner, and messages of support from the world of tennis and beyond.

"It disappoints me to know we live in a society where people like Ilie Nastase can make such racist comments towards myself and my unborn child, and sexist comments against my peers," Williams, 35, had said.

'Difficult' days

Nastase earned the nickname "Nasty" for his on-court outbursts and gamesmanship in his playing heyday in the 1970s.

But it also described his game, which earned him two Grand Slam singles titles and more than 100 ATP titles.

"I was five when I first picked up a racquet. Since then, tennis has been more than a sport or a profession for me. Tennis has been, and is, my life, and for tennis I have sacrificed almost everything, personal or professional," Nastase said in the statement.

"Unfortunately, now, in my 70s, I have somehow managed to do something I have never wanted or even imagined: to feel tennis moving further away from me. The last few days have been difficult for me."