The Wall Street Journal reports that both sides are set to meet Sunday (today) to get into the weeds of his $43 billion bid ... which he put forth publicly, and for which he also just announced he got legit financing in the amount of $46.5 billion to actually make it happen.

Per WSJ, Twitter is receptive to negotiating a deal ... or at the very least, hearing Elon out and considering a final price tag -- even though EM says he won't budge on $54.20-a-share.

There's more on the table, potentially than just dough. WSJ says Twitter honchos are mulling over a number of factors ... including a final valuation of what they think the bird app is worth, the possibility of inviting other bidders ... and maybe even insisting on Elon covering breakup costs if the would-be deal falls apart (aka, sweeteners).

As for why Twitter would even entertain this ... Reuters reports they're under pressure from shareholders who want to get paid out. Elon reportedly met with a select number of bigwig shareholders this past week to make his pitch on why Twitter would be better in his hands.

Among the things he reportedly wants to change (beyond his "free speech" objections) ... allowing for longer tweets, and pivoting away ads. He also reportedly told several of them ... you'll never reach my share price on your own. Twitter's closing price Friday was $48.93.

Reuters says some shareholders have expressed to leadership that not only should they talk to Elon and feel him out -- but, more importantly, see if they can finagle a larger offer.

Time will tell if Elon's willing to spend a bit more to take Twitter private -- but he almost had folks thinking he was ditching this whole endeavor, tweeting "Moving on" Sunday ... later clarifying that he meant teasing Bill Gates regarding climate change.