Sanders denies seeking primary challenge to Obama

Bernie Sanders says he's had some disagreements with President Obama, but did not work to gin up a Democratic primary opponent against him in 2012.

"I worked very hard to see Barack Obama elected," Sanders said Sunday on ABC's This Week.

Democratic opponent Martin O'Malley, who is trailing Sanders in polls as they both try to catch the front-running Hillary Clinton, has criticized the Vermont senator for talking about a primary challenge to the incumbent president in 2012.

"When President Obama was running for re-election, I was glad to step up and work very hard for him, while Senator Sanders was trying to find someone to primary him," O'Malley said during a Democratic forum on Friday.

In his ABC interview, Sanders noted that he discussed criticism of Obama on his radio show, and that in the run-up to 2012 he said people had the right to challenge the president if they wanted to.

But that doesn't mean he worked against Obama, and that idea is "categorically false," Sanders said.

"Barack Obama is a friend of mine," Sanders said.