RICHMOND, Va.  Senators Barack Obama and Joseph R. Biden Jr. seldom see each other as they campaign for the Democratic ticket. And they talk only occasionally. But on Wednesday, Mr. Obama delivered a long-distance message to his running mate.

“I think Joe sometimes engages in rhetorical flourishes,” Mr. Obama said, gently chiding the vice-presidential nominee as he sought to sweep aside a dustup Mr. Biden touched off when he predicted that a world crisis would test Mr. Obama during his first six months in office.

“A period of transition in a new administration is always one where we have to be vigilant, we have to be careful,” Mr. Obama said. “We have to be mindful that as we pass the baton in this democracy that others don’t take advantage of it  that’s true whether it’s myself or Senator McCain.”

In his remarks, Mr. Biden told supporters at a Seattle fund-raiser on Sunday that if Mr. Obama was elected, the world’s leaders would test his mettle as a young president, just as they did John F. Kennedy. The comment from Mr. Biden fanned a new line of criticism from Republicans that Mr. Obama is not ready for the presidency.