Mark Harmon by Cliff Lipson/CBS Mark Harmon by Cliff Lipson/CBS

Wondering why I've been skimping on the NCIS scoopage all these years? Well, I've been holding out for a biggie. And here it is:

Multiple sources confirm that Mark Harmon is embroiled in a tense standoff with NCIS executive producer Don Bellisario, with Harmon apparently threatening to walk. CBS declined comment, but an insider says Harmon has been unhappy for some time over Bellisario's "chaotic management style," and simply became fed up.

"Mark's been working every single day, 16 hours a day," whispers one source. "[Don] tries to micro-manage everything. Script pages get faxed to the set at the last minute, and Mark is tired of dealing with the huge impact that makes on his life. He doesn't have time for his family or anything when he's working hours like that."

It's unclear what impact the feud is having on the show's production schedule - technically speaking, Harmon has yet to miss a day of work - but my spy describes it as a "big standoff."

"Mark is one of the best-behaved actors in this industry," adds my mole. "He's a willing, hard worker and he doesn't complain easily. For him to [threaten a walk-out] means that the situation is very bad."

OK, NCIS fans, what's your take on all this? Can NCIS survive without Harmon? Or should Bellisario do whatever it takes to hold onto his leading man? Speak up! This may be the last NCIS scoop I have in a long time!