Jennifer Aniston's wedding guests are on standby for her big day.

The 44-year-old actress is reportedly set to marry Justin Theroux imminently and has told guests, including her mother Nancy Dow, who she was previously estranged from, to be prepared to move quickly once they receive information about the whereabouts of the extremely private celebration because they will only be given short notice.

A source told gossip website RadarOnline.com: ''Indications are it's going to be a small, private affair with just a select few invited. Those that are going have been told to expect a call at short notice, drop everything they are doing and head to the location when revealed.

''Guests have heard rumours about the wedding being held in Hawaii or even Greece - but most expect it to be staged in California.

''One person who has been told to expect a call is Jen's mom Nancy. She has been told to hang by the phone for a call any day now with all the arrangements.''

After being encouraged by Justin, Jennifer, who was previously married to Brad Pitt, has been steadily rebuilding her relationship with Nancy in recent years, who was hospitalised in November after falling and breaking her elbow and is still suffering from the effects of a stroke in 2011.

The insider said: ''John Melnick, Jen's half-brother, has kept Nancy up to date with everything that's going on as she continues to go from strength to strength after her recent hospitalisation.

''Nancy can't wait to be there at Jen's big day having missed out on her first wedding to Brad.

''Justin believes strongly in family values and has managed to convince Jennifer that, despite their differences in the past, Nancy deserves a wedding invitation.

''Nancy and Jennifer have had their ups and downs, but they're going to let bygones be bygones and she will be invited to her daughter's wedding ceremony.''

Other guests expected to attend are Jennifer's close pals Courtney Cox, Reese Witherspoon, Drew Barrymore, Chelsea Handler and Christine Taylor.