EXCLUSIVE

Alex Rodriguez says enough is enough -- he's been paying his ex-wife a king's ransom for a decade, his income has plummeted, she's now rich and he wants his support payments drastically reduced.

Sources connected to A-Rod tell us, the former Yankee has been locked in a spousal/child support war with Cynthia Scurtis for months. He's been paying $115,000 a month tax free in combined spousal and child support since the couple divorced in 2008. They have 2 daughters, 13-year-old Natasha and 10-year-old Ella.

We're told the agreement was always meant to be adjusted when A-Rod retired from the Yankees. A-Rod claims his income has dropped by 90% ... from $30 million a year, while he was on the Yankees, to around $3 million a year.

Our sources say Alex is especially vexed because he claims Cynthia is now a rich woman with millions in the bank, 3 homes and multiple cars. He grouses she has a master's degree in psychology yet chooses not to work. He also says she has a new child and a fiance, and he feels he's now bankrolling all of them.

A-Rod says the expenses for his 2 kids are somewhere between $7k - $12k a month, yet he's willing to pay $20k a month plus expenses for the kids, including tuition.

We're told Cynthia is negotiating, but wants nearly $50k a month so the ex-couple is at an impasse.