Dennis Rodman -- I Can't Pay My Child Support Bill ... Because I'm BROKE

2:18 PM PDT -- Rodman's rep tells TMZ ... the "sick" comment was a reference to the NBA legend's ongoing struggle with alcoholism.

The rep notes ... Dennis visited a doctor a few months ago and he's in "great physical shape."

Dennis Rodman can't afford to pay more than $800,000 in back child support ... because he's dead ass broke -- this according to new court documents.

Dennis' estranged wife Michelle Rodman filed new papers this month, claiming The Worm owes $808,935 in unpaid child support for his 9- and 10-year-old children -- and an additional $51,441 in unpaid spousal support.

But Dennis' attorney responded to the filing, insisting there's no way the Chicago Bulls legend can pay those bills -- because "Respondent Dennis Rodman is broke and cannot afford any additional fees."

According to his lawyer, Dennis is also "extremely sick" and just isn't making the same bank he made back in his heyday. The lawyer does not specify the nature of Rodman's illness.

According to Dennis' lawyer, the giant child support figure is based on an order Michelle obtained a while ago behind his back -- requiring Rodman to pay $50,000 a month in child support ... an order Dennis has been fighting since 2010.

Dennis' lawyer insists the monthly amount is "unjustified" because it isn't based on Dennis' actual income ... it's based on ludicrous estimates made by Michelle's attorney.