By Martyn Herman

RIO DE JANEIRO (Reuters) - American Alise Post's joy at winning a silver medal in the women's BMX final was tempered shortly afterwards on Friday as Australian husband-to-be Sam Willoughby finished off the podium.

Minutes after Post crossed the line second behind winner Mariana Pajon, she watched Willoughby launch off the start ramp bidding to go one better than the silver he won in London.

It was not to be though and he finished sixth despite winning each of his three semi-final laps.

"I'm proud of my U.S. team mates but my heart is with Sam," the 25-year-old told reporters after giving her fiance a consoling hug in the finish area.

"But it's BMX and its one of those sports where anything can happen. He rode a phenomenal effort. I guess we'll chat about it over dinner.

"It's funny I was kind of joking that I didn't want to one-up him today, I just wanted to match his London result so we could have matching hardware in the trophy room.

"But I'm very proud of him and myself. Obviously he's very disappointed."

(Reporting by Martyn Herman; Editing by Bill Rigby)