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Lucci will appear in at least two episodes of the Lifetime show, TV Line reports.
She is expected to play the wife of a retired general who ends up giving Claudia (Kim Delaney) advice when she discovers that she has a potential rival.
Meanwhile, TV Line says that Williams will play the rival - Jackie Clarke - and appear in at least seven episodes.
This is the first role for Lucci after All My Children came to an end earlier this year, though for a while she was linked to a part in Desperate Housewives.
Similarly, Williams's part in Army Wives will be her first big television role since the cancellation of Lie To Me earlier this year, although she had a recent guest spot in The Mentalist.
