WASHINGTON — It began two years ago as an idea by volunteers at a suburban Jewish community center and turned into a major international campaign, galvanizing everyone from President Barack Obama to the mayor of London.

And in case you haven’t heard yet about the movement to get the International Olympics Committee to hold a minute of silence to honor the 11 Israeli athletes and coaches slain at the Munich Games in 1972, NBC’s Bob Costas has promised to raise the issue and hold an on-air moment of silence in his Olympics broadcast.

The campaign for the commemoration gained steam in May, when IOC President Jacques Rogge denied a request by Israeli Deputy Foreign Minister Danny Ayalon for an official moment of silence during the Games to honor the Munich 11.

Costas told the Hollywood Reporter last week that as the Israeli team walks into the 80,000-seat Olympics stadium, he will say, “Many people find that denial more than puzzling but insensitive. Here’s a minute of silence right now.”

In making that pledge, Costas added his name to a growing list of public figures calling for the official IOC moment of silence. The list includes Obama and Republican presidential candidate Mitt Romney, the U.S. Senate, the German Bundestag, the Canadian and Australian parliaments, Australia Prime Minister Julia Gillard, 140 Italian lawmakers and some 50 members of the British Parliament. The Olympic Games’ opening ceremony is Friday.

On Sunday, London Mayor Boris Johnson unveiled a memorial plaque to the Munich victims at a ceremony near the Olympic village.

On Monday, the IOC’s Rogge surprised many by holding an impromptu moment of silence to honor the Munich 11 before delivering brief remarks in the Olympic Village, marking the first time the athletes have been memorialized inside in an Olympic Village.

Rogge spoke at an event for the Olympic Truce, a U.N.-backed initiative calling for an end to hostilities during the two weeks of the Olympic Games. IOC executive board members, special guests, Olympic athletes and officials attended the event.

“The 11 victims of the Munich tragedy… came to Munich in the spirit of peace and solidarity. We owe it to them to keep that spirit alive and to remember them.”

But two widows of the slain Israelis criticized the move to The Jerusalem Post as a public relations stunt and slammed Rogge for holding fast to his decision against an official commemoration.

The campaign for an official commemoration at the 2012 Games was born when Steve Gold and a few other volunteers at the Rockland County JCC in suburban New York decided to dedicate the Maccabi Games they were hosting to the murdered Israelis.

One of them knew Ankie Spitzer, wife of the Andrei Spitzer, an Israeli fencing coach killed in the attack, and asked her to record a video promoting a petition for an official IOC moment of silence. In the past, Olympics officials have attended private Israeli or Jewish ceremonies marking the tragedy, but other than the day after the murders themselves, the IOC has not held a commemoration of its own of the Munich massacre.

The petition was launched, and since April the signatures — and news stories about the effort — quickly mounted. At last count, some 104,000 people had signed on to the petition.

On Monday, Gold left for the London Games, where he, Spitzer and Ilana Romano – whose weightlifter husband, Yossef, was killed by the Palestinian terrorists in 1972 — plan to present their petition to Olympics officials.

The campaign gained visibility last week when Obama lent his support to the effort via an email from National Security Council spokesman Tommy Vietor to Yahoo! News, and this week when Romney — who was CEO of the 2002 Winter Games at Salt Lake City — threw his support behind the effort.

Gold, who was the first person to sign the petition, credited Jewish and non-Jewish organizations with picking up on the effort.

“Everybody knows somebody. There was not one organization that said they would not help us,” he said. “To them this was a no-brainer, and everybody started putting it on their website, whether it was the Anti-Defamation League or the Board of Rabbis or the Jewish Federations of North America. So it began to go viral. It’s cool stuff.”