Non-circumcised man leading prayers

If a man or woman becomes Muslim after the age of thirty or thereabouts, do they have to be circumcised? Is a man who is not circumcised permitted to lead the prayer?

Praise be to Allah, and blessings and peace be upon the Messenger of Allah:

Circumcision is a part of sunan al-fitrah (actions befitting the natural state of man) for men and women, but if it is not done after a person is fully-grown, there is nothing to worry about. As for a non-circumcised man leading the prayers, this is valid.