By Frances Harrison
Religious affairs correspondent, BBC News
Sikh representatives are refusing to take part in an interfaith meeting with Pope Benedict XVI when he visits the US next month.
Sikhs wear the kirpan as an article of faith
The problem is that the US secret service will not allow the Sikhs to wear the kirpan, or ceremonial dagger.
The dagger symbolises Sikhs' commitment to resist oppression and injustice.
Although Jews, Hindus, Muslims and Buddhist representatives will be there, the Sikhs are being replaced by representatives from the Jain religion.
A statement from the World Sikh Council said it was disappointed the secret service had not been able to respect the religious rights of Sikhs.
It said representatives would not able to attend the meeting in Washington if it meant renouncing a fundamental tenet of their faith.
A spokesman for the secret service has been quoted as saying that it understood the dagger was a religious object for Sikhs, but that, by definition, it was also a weapon.