Christian Slater felt competitive towards James Franco over sex scenes in the new film 'King Cobra.'

Christian Slater

Christian Slater

The 47-year-old actor admitted he didn't want his co-star to be better in the intimate scenes than his co-star in the new crime-drama film based upon the book 'Cobra Killer.'

Speaking about the upcoming blockbuster during a Q&A at the ICF film premiere, he said: "James was going to be doing the lion's share of the sexual aspects [of the film] and then I got competitive... We even improv'd some stuff.

"OK, I'll stop - but yeah, great direction!"

'King Cobra' is based on the real story of Bryan Kocis who was murdered in 2007.

Meanwhile, Justin Kelly has revealed the film includes spontaneous scenes, which weren't penned in the script.

Speaking about Christian and Garrett's moment in the film, Kelly said: "[Christian] pushes him up against the closet door... That was not written or planned. That [was] Christian saying, 'Where's my gay sex scene?' "

Meanwhile, Slater has revealed he accepted the project because he was desperate to play a role in something, which "scared" him because it was out of his "comfort zone".

Speaking previously, he said: "I was looking for something to do that scared me. Something that was out of my comfort zone. It didn't feel stereotypical and there were aspects of the character that I felt I could really identify with. It really spoke to me."

However, he also signed up to the project because he was always been a "huge fan" of the '127 Hours' star.

He explained: "Well, I'd worked with James Franco a couple years ago on 'Adderall Diaries' and I've always been a huge fan of his. And he presented me with this and I got excited by it. I don't think any of us expected this to be a 2,000-screen, $100-million opening weekend type of release, but I was thrilled that James was supporting a young director like [Justin Kelly] to make this risky, exciting film."