3:07 PM PT -- Elon Musk might need more time to train and get ready for a cage match against Mark Zuckerberg -- but the Facebook founder says he's ready now.

Zuck fired back at Elon's chirping this weekend, taking to his own platform (Threads) to point out that he's all set to rumble, and at a moment's notice. He also says he suggested a date of August 26 when Elon first challenged him -- but claims EM is stonewalling.

Finally, MZ takes a jab at Elon's proposal of streaming the bout on X -- suggesting Threads would be a better place for generating actual revenue (for charity). Twitter/X has been in dire financial straits for months now.

Elon's teased the fact that he's pumping iron in preparation, but also notes ... Mark probably has him beat on stamina -- and that if they duke it out, he'd wanna end it quickly.

Elon Musk plans to make some loot for his company formally known as Twitter, because he's planning on live-streaming his highly anticipated fight with Mark Zuckerberg on X ... so he declared Sunday.

TMZ has been reporting, Zuck and Musk are both all in for mixing it up in the UFC octagon.  There were actually talks between UFC and the Italian Foreign Ministry about holding the fight at the Coliseum, but our sources say that's not going to happen.

We're also told if the fight goes down, it will likely take months. We're surmising from what we're hearing Elon needs more time to train ... something Zuck has been doing for a long time.

Despite their height and weight disparity -- Zuck's 5'7" and 150 lbs, while Musk towers over him at 6'2" weighing 230 -- M.Z. had a big edge when it comes to stamina.

The more these guys jawbone back and forth, the more likely it is they'll fight, because neither one is prone to blinking.

Stay tuned.