Sir Ian McKellen is ''going to marry'' Patrick Stewart.

The 73-year-old actor will officiate at the ceremony between his friend and 'X-Men' costar and his fiancee, jazz singer Sunny Ozell, when they tie the knot in Masachusetts.

He said: ''I'm going to marry Patrick [Stewart]. I am going to officiate at his wedding.

''In Massachusetts, in the middle of America somewhere, you get a friend along, and I read out the words, and Sunny and Patrick will then be married.''

The British actor revealed it won't be the first time he has officiated at such a service.

Speaking on an upcoming episode of 'The Jonathan Ross Show', he added: ''I've done it once before with two guys having a civil partnership. I was crying my eyes out.

''I wore a white gown which I bought in India. You mustn't upstage the bride.''

Massachusetts' Secretary of Commonwealth offers a service that allows a family friend or relative to perform a couple's wedding ceremony for a fee of $25.

Patrick, 72, and Sunny, 35, have been dating since 2009.