Veteran NBA player Jason Collins announced Monday that he is gay -- the first athlete from one of the four major U.S. professional sports leagues to do so.

Collins made the announcement in an essay published in the May 6 issue of Sports Illustrated.

“I’m a 34-year-old NBA center,” Collins wrote. “I’m black. And I’m gay.”

Collins, who played for both the Boston Celtics and the Washington Wizards this past season, said he did not intend to become the first openly gay athlete in a major league sport.

“But since I am, I’m happy to start the conversation,” he 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.”

Shortly after Collins’s column was published on Sports Illustrated’s website, NBA players and celebrities of all stripes took to Twitter to express their support.

“Proud of @jasoncollins34,” Los Angeles Laker forward Kobe Bryant tweeted. “Don’t suffocate who u r because of the ignorance of others #courage #support #mambaarmystandup #BYOU.”

“The time has come,” Laker forward Steve Nash tweeted. “Maximum respect.”

In a statement posted to Twitter, NBA Commissioner David Stern called Jason and his twin brother, Jarron, “exemplary members of the NBA family.

“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.” #NBAFamily

Former U.S. president Bill Clinton tweeted that he is, “proud to call Jason Collins a friend.”

In a statement, Clinton said he has known Collins since he was a classmate of his daughter, Chelsea, at Stanford.

“Jason’s announcement today is an important moment for professional sports and in the history of the LGBT community,” Clinton said.

“It is also the straightforward statement of a good man who wants no more than what so many of us seek: to be able to be who we are; to do our work; to build families and to contribute to our communities. For so many members of the LGBT community, these simple goals remain elusive. 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.”

Collins’s former Stanford roommate, Rep. Joe Kennedy III of Massachusetts, also issued a statement to congratulate his friend.

“For as long as I’ve known Jason Collins, he has been defined by three things: his passion for the sport he loves, his unwavering integrity, and the biggest heart you will ever find,” Kennedy said. “Without question or hesitation, he gives everything he’s got to those of us lucky enough to be in his life. I’m proud to stand with him today and proud to call him a friend.”

In his column, Collins wrote of feeling jealous when Kennedy told him he marched in Boston’s Gay Pride Parade last year.

“I was proud of him for participating but angry that as a closeted gay man I couldn't even cheer my straight friend on as a spectator. If I'd been questioned, I would have concocted half truths. What a shame to have to lie at a celebration of pride,” Collins wrote.

“I want to do the right thing and not hide anymore. I want to march for tolerance, acceptance and understanding. I want to take a stand and say, ‘Me, too.’"

A few weeks ago, Collins revealed his homosexuality to Kennedy, and the two plan to march in this year’s Boston pride parade on June 8.

Collins said that he actually began seriously thinking about coming out during the 2011 lockout. He said the interruption to his daily routine “forced me to confront who I really am and what I really want.”

The first person he told, his aunt Teri, reacted by saying she had known “for years” that he was gay. 

He only revealed his homosexuality to his twin brother last summer, Collins said, adding his brother “was downright astounded.

“He never suspected. So much for twin telepathy. But by dinner that night, he was full of brotherly love. For the first time in our lives, he wanted to step in and protect me.”

Collins, a free agent, also said he would like to continue playing in the NBA.

There has been much speculation about whether an athlete from one of the big four major league sports would soon reveal he was gay.

Former Baltimore Ravens linebacker Brendon Ayanbadejo, who is an outspoken advocate for gay rights and marriage equality, told a Baltimore Sun reporter a few weeks ago that “up to four” National Football League players could come out at the same time.

Ayanbadejo has said he would not out any players, but said he has been working with football players in addition to athletes in other sports to devise support systems in the event that they decide to reveal they are gay.