Meryl Streep is set to join the cast of 'Mary Poppins Returns'.

The Oscar-winning actress is said to be in talks to take on the role of Mary's cousin, Topsy, who didn't appear in the 1964 classic.

According to Variety, if negotiations are successful, Meryl will be singing in her role in the hugely-anticipated sequel, just as she did in 'Into the Woods' and 'Mamma Mia!'.

The film will see Emily Blunt, 33, take on the leading role of Mary Poppins, the character made famous by Julie Andrews.

The 'Huntsman: Winter's War' actress will play the magical nanny who, in the original film, acted as guardian for children Jane and Michael Banks taking them on 'Supercalifragilisticexpialidocious' adventures.

It will be released in December 2018 and will focus on some of the material featured in P.L. Travers' seven additional novels.

An official synopsis for the movie reads: ''In Depression-era London, a now-grown Jane and Michael Banks, along with Michael's three children, are visited by the enigmatic Mary Poppins following a personal loss. Through her unique magical skills, and with the aid of her friend Jack, she helps the family rediscover the joy and wonder missing in their lives.''

The new character of Jack, a street lamp lighter, will be played by Lin-Manuel Miranda.

The movie will be directed by Rob Marshall, who previously worked with Blunt on 'Into the Woods', and he is thrilled to be a part of the project.

Marshall said: ''I am truly humbled and honoured to be asked by Disney to bring PL Travers' further adventures to the screen.

''The iconic original film means so much to me personally, and I look forward to creating an original movie musical that can bring Mary Poppins, and her message that childlike wonder can be found in even the most challenging of times, to a whole new generation.''

'Mary Poppins' which starred 'Dick Van Dyke' as Chimney Sweep Bert, won five Oscars, including Best Actress for Julie Andrews.