Star wars brewing between ROBERT DE NIRO and JOHN TRAVOLTA on the set of their new flick “Killing Season!”

Said My Spy Onda Lottalot: “They’re cordial to each other, but there’s much tension – and it’s mostly a matter of style. De Niro arrives each morning alone – while John always shows up with an entourage of six or seven people.

"But their worst clash was over how to film a fight scene!” The script called for the stars to start fighting, roll down a hill into a stream – then keep battling in the water.

“Travolta wanted a stuntman because the water was cold, and he didn’t want to hurt himself rolling down the hill,” said the source.

“But De Niro, 10 years older than his co-star at 68, was livid over Travolta’s refusal to do the scene. After lots of negotiating, John finally agreed to get in the water – but flatly refused to roll down the hill.

"De Niro’s not happy!”