Khloe Kardashian's Trigger For Divorce ... She Wants Kids

Khloe Kardashian told Lamar Odom she needed to end their marriage once and for all ... because the clock is ticking and she wants kids ... sources connected to the former couple tell TMZ.

Our sources say Khloe sat Lamar down recently and explained she wanted a family, and couldn't even start the process of looking until she was single again.

We're told Khloe made it clear to Lamar from the time he almost died last year ... she was dropping the divorce because she wanted to help him get better. She vowed not to re-file until he was able to run his own life day-to-day, and she believes he's at that point right now.

Khloe has made it clear to friends and family ... there has never been a romantic relationship since she filed for divorce the first time around in December 2013.

Lamar, we're told, completely understood, and the 2 vow to remain friends, and Khloe has promised she'll help him whenever he needs it.