President Obama, in a heavily partisan speech defending his signature health care law, claimed Thursday "there's no widespread evidence" it is hurting jobs -- despite widespread reports that businesses are cutting back worker hours in order to avoid extra costs tied to the law.

The charge that ObamaCare is driving Americans into part-time work is one of the central claims that opponents make in arguing for the law to be defunded or delayed. Sen. Ted Cruz, R-Texas, reiterated the claim during his 21-hour floor speech against ObamaCare this week.

But the president, while promoting the law to a friendly audience in suburban Washington, brushed off the argument.

"Most of the stories you'll hear about how ObamaCare just can't work, they're just not based on fact," Obama said.

He continued: "They said this would be a disaster in terms of jobs. There's no widespread evidence that the Affordable Care Act is hurting jobs. ... Reforming health care's going to help the economy over the long-term."

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The claim flies in the face of what union leaders have been telling the White House and Democratic lawmakers for months.

In a widely noted letter to Democratic leaders over the summer, the heads of the Teamsters and other unions argued that "perverse incentives" were hurting jobs.

Unless the law is changed, they wrote, "the ACA will shatter not only our hard-earned health benefits, but destroy the foundation of the 40-hour workweek that is the backbone of the American middle-class."

They, and employers across the country, point to provisions of the law that would require businesses with 50 or more full-time workers to provide health insurance to those workers. The argument is that businesses are scrambling, then, to make more workers qualify as part-time, by reducing their hours to fewer than 30 a week.

"Numerous employers have begun to cut workers' hours to avoid this obligation, and many of them are doing so openly," the union leaders wrote.

The Obama administration, in a surprise move, delayed the employer mandate by a year. But that hasn't stopped businesses from cutting hours.

Investor's Business Daily has compiled a list of more than 300 employers that have cut worker hours or staffing levels, many as recently as this month.

Among them was SeaWorld, in Florida, cutting back part-time hours from 32 to 28 per week.

The Washington Free Beacon reported Wednesday on a South Carolina cleaning business claiming it will hire only part-time workers in order to stay under the 50-worker threshold.

Obama was promoting the law in Maryland in advance of the Oct. 1 launch of the so-called insurance "exchanges." These are regulated marketplaces where Americans will be able to shop for approved insurance plans -- enrollment begins Tuesday.

Obama tried to counter "misinformation" about the law, and noted: "If you already have health care, you don't have to do anything."