New York: Michael Sam made history on Saturday as the St Louis Rams made him the first openly gay player to be drafted into the National Football League.

Sam had an agonisingly long wait for the milestone moment, which came as the seventh and final round of the three-day draft was winding down.

“I knew I was going to get picked somewhere,” said Sam, who starred as a defensive end for the University of Missouri and went public with his sexuality in February.

“Every team that passed me, I was thinking how I’m going to sack their quarterback.”

The 24-year-old was taken with the 249th overall selection in the annual allocation of new talent for America’s most popular sport — seven spots before the draft concluded with pick No 256.

Cameras of broadcaster ESPN captured Sam’s emotional reaction to the telephone call he received from Rams head coach Jeff Fisher.

Sam — watching the draft on television with family and friends far from the event’s headquarters at New York’s Radio City Music Hall — broke down in tears while speaking with Fisher.

Soon after, Sam was beaming in a photo he posted on Twitter.

“Thank you to the St Louis Rams and the whole city of St Louis,” he tweeted. “I’m using every [ounce] of this to achieve greatness!!”

Fisher told ESPN that the team was mainly focused on what Sam can contribute on the field, but he acknowledged the groundbreaking nature of the selection.

“In the world of diversity we live in now, I’m honoured to be part of this and I’m excited about his opportunity to help this football team win,” Fisher said.

President Barack Obama congratulated Sam in a statement released to United States media.

“The president congratulates Michael Sam, the Rams and the NFL for taking an important step forward today in our nation’s journey,” the White House statement read, adding that lesbian, gay, bisexual and transgender Americans “prove every day that you should be judged by what you do and not who you are.”

Sam, 24, became the first openly gay man to be drafted into one of America’s major professional sports leagues.

Veteran NBA player Jason Collins was not with a team when he came out as gay last year, but is now playing for the Brooklyn Nets.

In revealing his sexuality, already known to his university teammates, Sam had said he hoped to be judged not as a social trailblazer but as a football player.

But his presence among the prospects in the draft made the final day — usually the preserve of diehard fans — a widely watched affair.

“So proud of the @STLouisRams for showing there’s nothing to be afraid of,” gay comedian and chat show host Ellen DeGeneres wrote on Twitter.

As a senior at Missouri, Sam notched 11.5 sacks and 19 tackles for losses as he earned first-team All-American honours and was named Southeastern Conference Defensive Player of the Year.

However, his draft stock dropped after a disappointing showing at the NFL scouting combine, where teams evaluate potential new players.

At 6ft 2in and 256 pounds (1.88m, 116kg), Sam is also small for an NFL defensive end. That had draft pundits predicting Sam would not be taken until the sixth round of the draft.