Seinfeld star Jason Alexander sorry for revealing behind-the-scenes goss

Jerry Seinfeld and Jason Alexander starred on the TV show Seinfeld. Photo / Getty Images

Seinfeld star Jason Alexander has apologised after saying the actress who played his fiancee on the hit comedy show was impossible to work with.

Alexander's character George Costanza was engaged to Susan Biddle Ross, played by Heidi Swedberg, but she dies after licking cheap wedding invitation envelopes.

Earlier this week, Alexander told US radio presenter Howard Stern Swedberg was a lovely person, but their instincts for comedy were mismatched and that's why she was killed off.

Alexander said he would complain to his co-stars and series co-creator Larry David at dinner each week.

"I kept saying, 'I am going out of my mind, you guys are killing me, I can't understand how to play off of this girl,'" he told Stern.

He said his colleagues reassured him things were fine until Jerry Seinfeld (playing a semi-fictitious version of himself) and Julia Louis-Dreyfus (Elaine Benes) had to film lots of scenes with Swedberg one week.

"They did the week and we got to the restaurant afterwards and they go, 'You know what? It's f***ing impossible,'" Alexander said.

"Julia actually said, 'I know, don't you want to just kill her?'

"Larry went, 'Ka-bang, pow, we have to kill her'."

Now, Alexander has apologised for his comments in a lengthy Twitter posting.

Oh dear God, leave Heidi alone

Read: http://t.co/14Q5akRj38

— jason alexander (@IJasonAlexander) June 4, 2015

"To Heidi, I personally apologize. You are a sweetheart," he wrote.

"She is a kind, lovely person who undoubtedly worked really hard to create Susan and that character was clearly what Larry and Jerry wanted her to be for George. I just felt I was on uncertain ground in how to play off that character and I was always concerned that it wasn't working. And that's what I would voice concern about.

"I feel officially awful."

- AAP with nzherald.co.nz