Rachel McAdams doesn't know if she wants to get married.

The 'Vow' actress - who was previously engaged to Ryan Gosling - has been dating actor Michael Sheen for 18 months but isn't sure whether she is ready to make their relationship more serious.

Asked if she is ready to get married, she said: ''Hmmm. That's something that I'm not going to answer right now because right now I don't know what The Answer is.''

However, she did admit she has always wanted to marry and have children.

She said: ''[Getting married and having children] is something I've always wanted.''

Despite her uncertainty, Rachel believes marriage is one of the most ''romantic and strong'' gestures a person can make.

She told Britain's HELLO! magazine: ''A friend just got married to a guy she'd known for six years and had been living with for a long time. She was such a ball of nerves!

''She loves the guy and at first I was thinking, 'Isn't this part just the formality?' Then I realised there's a big difference between whispering sweet nothings when it's just the two of you and getting up and making the promise in front of all the people you love, who will be in your life for the rest of your life. I think that to make a public vow is a really romantic and strong gesture.''