DENVER -- Another former Republican presidential candidate has descended on this city to cast Barack Obama as unready for the White House.

Giuliani was joined by Michael Steele, the former lieutenant governor of Maryland, who attacked Obama for voting against a troop funding bill last year in Congress, calling the presumptive Democratic nominee "woefully ill-prepared to be the next president." Obama opposed the bill because it lacked a timetable for withdrawing troops from Iraq, but Biden supported it.

"Senator Biden agreed that Barack Obama was unprepared to be president," the former mayor said. Giuliani's news conference, one of several events Republicans have organized in Denver, was held a few miles from where Obama will accept the Democratic nomination on Thursday.

Referring to Obama's pledge last fall to meet with leaders of hostile governments, including Iran, without preconditions, Giuliani said, "I think Hillary Clinton called it naive; Senator Biden called it irresponsible."

Obama has said he would make sure any meeting he held with foreign leaders would advance U.S. interests. And both Clinton and Biden have enthusiastically affirmed their support for Obama in recent days.

But Giuliani and other Republicans have seized on what they argue was a glaring omission in Clinton's convention speech: She didn't say Obama is "ready" to be president, something she challenged during the primaries. "She left out the key question that lingers," Giuliani said. "What we don't know is if she thinks he's qualified to be commander in chief."

Ann Lewis, a longtime adviser to Clinton, dismissed Giuliani's argument in an interview a few hours after Giuliani's news conference, and said that, in her speech, the senator from New York was trying to give the most compelling argument she could for her supporters.

"Of course she believes he is ready to be president and ready to be commander in chief," Lewis said.