Basketball center Jason Collins on Monday became the first active player in a major American professional team sport to reveal he is gay -- a groundbreaking disclosure greeted with broad support.

Collins, a 34-year-old free agent who has played for six NBA teams over the past 12 seasons, went public with his sexuality in an essay published on Sports Illustrated magazine's website.

"I didn't set out to be the first openly gay athlete playing in a major American team sport. But since I am, I'm happy to start the conversation," Collins said.

"I wish I wasn't the kid in the classroom raising his hand and saying, 'I'm different.' If I had my way, someone else would have already done this. Nobody has, which is why I'm raising my hand."

Among those backing Collins was US President Barack Obama. A White House aide told AFP: "The President called Jason Collins to express his support and said he was impressed by his courage."

The revelation will focus attention on Collins and has drawn comparisons to the way the spotlight shone on Jackie Robinson in 1947 when he Major League Baseball's first black player.

"Jason Collins has forever changed the face of sports," said Human Rights Campaign president Chad Griffin. "No longer will prejudice and fear force gay athletes to remain silent about a fundamental part of their lives.

"Collins has courageously shown the world that one's sexual orientation is no longer an impediment to achieving one's goals, even at the highest levels of professional sports ... Jason Collins is a hero for our own times."

Collins can expect homophobic taunts from NBA game hecklers the way Robinson endured racial insults without fighting back.

"I don't mind if they heckle me. I've been booed before," Collins said.

"Everyone is terrified of the unknown, but most of us don't want to return to a time when minorities were openly discriminated against."

Golden State Warriors president Rick Welts, the highest-ranked NBA executive who is openly gay, said he was confident Collins would not have trouble landing a new contract because of his admission.

"He absolutely will receive more opportunities. More doors will open than close," Welts said on Twitter. "I'm very proud of him. It was very courageous. This was an important step.

"There might be other athletes ready to take this step. We'll wait and see," Welts said. "It still is a big deal today. There will be a day when it isn't."

Collins said he had no clue how his next NBA teammates might react knowing they share the locker room with a gay man.

"I'm a pragmatist. I hope for the best, but plan for the worst," Collins said. "I'm a veteran and I've earned the right to be heard. I'll lead by example and show that gay players are no different from straight ones."

Former US president Bill Clinton, whose daughter Chelsea was a college friend of Collins at Stanford, lauded Collins' disclosure as historic.

"Jason's announcement today is an important moment for professional sports and in the history of the LGBT (Lesbian-Gay-Bisexual-Transgender) community," Clinton said.

"I hope that everyone, particularly Jason's colleagues in the NBA, the media and his many fans extend to him their support and the respect he has earned."

NBA commissioner David Stern praised Collins for the courage and leadership of his admission.

"Jason has been a widely respected player and teammate throughout his career and we are proud he has assumed the leadership mantle on this very important issue," Stern said.

Collins also earned support from fellow NBA players, teammates, celebrities and other gay athletes such as retired NBA player John Amaechi and tennis legend Martina Navratilova.

"Jason Collins showed a lot of courage today," Miami Heat guard Dwyane Wade said. "I respect him for taking a stand and choosing to live in his truth."

Collins, a 7-footer who helped New Jersey reach the 2002 and 2003 NBA Finals, has averaged 3.6 points and 3.8 rebounds over 713 NBA games for New Jersey, Memphis, Minnesota, Atlanta, Boston and Washington.

But he has mainly played in reserve roles over the past six seasons.

Collins wore jersey number 98 this past season to honor Matthew Shepard, who died in 1998 after being the victim of an anti-gay hate crime, while averaging 1.1 points and 1.6 rebounds over a combined 38 games for Boston and Washington.

"When I put on my jersey I was making a statement," he said.

"I still love the game and I still have something to offer. My coaches and teammates recognize that," Collins said. "At the same time, I want to be genuine and authentic and truthful."

Collins said years of keeping his sexuality secret took a toll.

"It takes an enormous amount of energy to guard such a big secret," Collins said. "I've endured years of misery and gone to enormous lengths to live a lie. I was certain that my world would fall apart if anyone knew.

"Each time I tell another person, I feel stronger and sleep a little more soundly."