(Reuters) - U.S. politicians and relatives of 11 Israeli team members killed at the 1972 Munich Olympics refused to be deterred on Wednesday in their campaign for a minute´s silence at the opening ceremony in London to honor the dead.

The issue is proving a diplomatic headache for International Olympic Committee (IOC) President Jacques Rogge, who hoped to end the debate with a surprise tribute to the victims in the Olympic village in London on Monday.

Campaigners have said the gesture was not adequate and it was time for the IOC to honor the victims in Friday´s opening ceremony, expected to be watched by more than a billion people around the globe.

IOC claims that it wanted to keep put of politics rang hollow, they said, accusing it of pandering to Israel´s enemies in the Middle East.

"They (the IOC) are afraid of offending, frankly, some of the Arab nations," U.S. Congressman Eliot Engel told reporters on a conference call.

U.S. President Barack Obama and Republican rival Mitt Romney have both backed calls for a moment of silence.

Ankie Spitzer, whose husband Andrei was killed in Munich, was planning to meet Rogge in London on Wednesday to hand over a petition signed by more than 100,00 people.

Steve Gold, who helped to lead the petition, said there could be a spontaneous demonstration among the 60,000 people in the Olympic Stadium on Friday if Rogge did not change his mind.

The Munich massacre was the worst attack on the Olympic Games. Palestinian guerrillas from the Black September group broke into the Israeli section of the Olympic village by scaling a perimeter fence with weapons concealed in sports bags.

Demanding the release of Palestinian prisoners held in Israeli jails, they initially killed two hostages. Within 24 hours, another nine Israelis, five Palestinians and a German policeman were dead after a standoff and subsequent botched rescue effort.

Security has been transformed in the ensuing four decades and more than 17,000 British troops will help to guard the London Games. (© Thomson Reuters 2012. 07/25/12) (Editing by Sonya Hepinstall)