By PATRICIA TOWLE

Reese Witherspoon was all smiles when she won the Oscar for Best Actress — but at home, she has been trying to save her marriage to Ryan Phillipe.

Friends say the 29-year-old mom of two is even planning to have baby #3 — and she'll walk away from her red-hot $30m a movie career if she has to!

Said an insider: "Reese has achieved everything a woman could want except for a rock-solid marriage. She's on Cloud Nine with her Oscar win, but she knows that her marriage to Ryan could use strengthening. She'd gladly put her career on hold because family matters most."

The Nashville native, who won the top prize for her portrayal of Johnny Cash's wife June Carter Cash in Walk The Line, married 31-year-old Ryan in 1999.

It was just three months before the birth of their daughter Ava Elizabeth.

In the past, their rocky marriage seemed in danger of crumbling at times. Now friends say the couple have overcome their hard times.

Said the insider: "Like June — who fought to save her marriage to Johnny — Reese is a fixer who will never let go of her man.

"When Ryan was spied flirting with other women earlier in their marriage, Reese hauled him off to couple's counseling and later became pregnant with second child, Deacon, who's now two.

"She's now hoping that same strategy will shore up her marriage once and for all."