20/04/2012 07:48 BST

Michelle Williams And Jason Segel Make Their Public Debut As A Couple

Michelle Williams and Jason Segel have finally gone public with their long-rumoured romance.

The pair made their debut as a couple as they attended an afterparty together for Jason's new film The Five Year Engagement on Wednesday night.

Although Michelle skipped the red carpet earlier in the evening, she was there to support her beau for the premiere at the Tribeca Film Festival.

A source, who spotted the pair together at the afterparty at the Museum of Modern Art in New York told Us Weekly magazine: "Michelle was really sweet but her usual shy self in crowds - she stayed close to Jason and only really engaged in conversation with people that she knew. Jason would put his arms around her waist and they gave each other a few sweet pecks - they definitely seemed to have a physical chemistry."

After the pair were recently spotted hand-in-hand near Michelle's Brooklyn home, Jason confirmed to US news show Extra: "I think we would just very much like to be happy. That's all I'm going to say about it."

Michelle was previously engaged to late actor Heath Ledger, the father of her six-year-old daughter Matilda.

IN PICS: Five-Year Engagement Premiere

'Five-Year Engagement' Premiere