Washington, Sep 7 (IANS) US President Barack Obama has caused quite a flutter by accusing his Republican opponents of talking about him "like a dog" at a rally to launch his embattled Democratic party's election campaign.

"Some powerful interests who had been dominating the agenda in Washington for a very long time and they're not always happy with me," he said addressing a union crowd on Labour Day Monday in Milwaukee, Wisconsin.

"They talk about me like a dog. That's not in my prepared remarks, but it's true," he told the union crowd straying from his prepared remarks to take a more aggressive tone in campaign mode.

"They're betting that between now and November, you'll (voters) come down with a case of amnesia," Obama said in the speech less than two months ahead of midterm elections where Democratic majorities in the House and Senate are on stake.

"They (Republicans) think you'll forget what their agenda did to this country. They think you'll just believe that they've changed. These are the folks whose policies helped devastate our middle class and drive our economy into a ditch. And now they're asking you for the keys back," he said with some bitterness, alluding to the recent tirade launched against him by his critics.