The latest Republican effort to repeal the Affordable Care Act would inflict "real human suffering" on millions of Americans, President Obama said Wednesday, speaking out in public defense of his signature healthcare reform effort.

The law has led to major increases in the number of Americans with healthcare coverage, Obama said, speaking in New York at an event on global development sponsored by the Bill and Melinda Gates Foundation.

"When I see people trying to undo that hard-won progress for the 50th or 60th time," he said, "it is aggravating."

The Republican efforts would make coverage unavailable to cancer survivors, pregnant women, children with asthma and others with existing medical problems, he said, "without any ... common sense rationale."

"It's certainly frustrating to have to mobilize every couple months to keep our leaders from inflicting real human suffering on our constituents," he added. "But typically, that's how progress is won, and how progress is maintained."