Former US president Bill Clinton dropped a hint Monday that the end might be nigh for his wife Hillary's dogged campaign for the Democratic White House nomination, according to reports.

"I want to say also that this may be the last day I'm ever involved in a campaign of this kind," the former US president told Clinton supporters in South Dakota, ABC and NBC reported on their news websites.

"I thought I was out of politics, till Hillary decided to run. But it has been one of the greatest honors of my life to go around and campaign for her for president," he added at the start of his stump speech.

Former US President Bill Clinton speaks during a campaign event for his wife Democratic presidential hopeful Sen. Hillary Rodham Clinton, D-N.Y., Sunday, June 1, 2008, in Great Falls, Mont. [Agencies]