The 52-year-old actress, whose most famous credits include Sleepless in Seattle and When Harry Met Sally, will play a role similar to that of 'Future Ted' in How I Met Your Mother, which was voiced by Bob Saget.

Once known as America's sweetheart while being the go-to leading lady for rom-coms in the 1990s, in recent years Ryan has lacked a big-screen hit. Her most recent efforts have been to collaborate with Friends' actor Lisa Kudrow's on the latter's Web Therapy comedy series.

With the hugely popular HIMYM ending in March after nine seasons - and to mixed responses on the final plot twist - a buzz has been brewing about the spinoff, which will be written by Modern Family's Emily Spivey and the sitcom's original creators Carter Bays and Craig Thomas.

Indie favourite Greta Gerwig, who starred in Frances Ha, has signed up as the lead role of Sally, who is facing a split from her husband and turns to her circle of friends.

Network CBS will be hoping to mimic the magic of the original, the finale of which garnered the show's highest ever US ratings with 13.1 million viewers.

The pilot is likely to air later this year.