(CNN) -- Sen. John McCain strongly criticized Sen. Barack Obama Wednesday for not visiting Iraq in more than two years and for turning down the Arizona senator's suggestion that the two should make a joint trip to the country.
"Sen. Obama has been to Iraq once -- a little over two years ago he went and he has never seized the opportunity except in a hearing to meet with Gen. [David] Petraeus," McCain said at a campaign event in Reno, Nevada. "My friends, this is about leadership and learning."
Again raising the issue of Obama's willingness to meet with Iranian President Mahmoud Ahmadinejad, McCain also said of the Illinois senator, "He wants to sit down with the president of Iran but hasn't yet sat down with Gen. Petraeus, the leader of our troops in Iraq?"
Obama last visited Iraq in January, 2006 for a two-day tour of the country.
McCain's comments come the same day the Republican National Committee launched a clock on its Web site noting how many days it has been since Obama traveled to Iraq, and three days after his supporter Sen. Lindsey Graham, R-South Carolina, suggested the presumed Republican nominee and Obama tour the country together. 
Watch more of McCain's criticism of Obama »
McCain later said he agreed the Democratic presidential contender should accompany him on an upcoming trip, adding that he would "seize that opportunity to educate Sen. Obama along the way."
Obama spokesman Bill Burton declined the invitation and called the move a "political stunt."
"The American people don't want any more false promises of progress, they deserve a real debate about a war that has overstretched our military and cost us thousands of lives and hundreds of billions of dollars without making us safer," he added.
Speaking Wednesday, McCain called those comments a "profound misunderstanding of what's happened in Iraq and what's at stake in Iraq."
"Because if we set a date of withdrawal as Sen. Obama wants to do, there will be chaos, there will be genocide, there will be increased Iranian influence there, and we will have to go back with further sacrifice of American blood and treasure."
Also Wednesday, Obama's campaign used former White House Press Secretary Scott McClellan's new book attacking the Bush administration as a means to take a swipe at McCain, connecting what Obama called "the failed Bush policies" to McCain.
"It's not news that this administration engaged in spin and deception to lead us into a war that should've never been authorized and never been waged," Obama spokesman Hari Sevugan said.
"The only question now is do we continue George Bush's failed policy in Iraq or do we change it? John McCain is promising four more years of the exact same policy in Iraq that asks everything of our brave troops and nothing of the Iraqi government, while Barack Obama wants to begin a phased withdrawal of our troops and refocus our efforts on going after al-Qaeda in Afghanistan."
Asked for an on-camera response from Obama Wednesday, a senior aide refused.
Meanwhile, Sen. Hillary Clinton stepped up her efforts to convince potential voters and the party's superdelegates that she is a stronger general election candidate than Obama.
In a speech Tuesday night at a Montana campaign event, the New York senator suggested Obama is much more likely to lose to McCain in the fall.
"We have not gone through this exciting unprecedented historic election only to lose," Clinton said at an event in Billings, Montana.
"You have to ask yourself who is the stronger candidate?" she continued. "And based on every analysis of every bit of research and every poll that's been taken and every state that a Democrat has to win, I am the stronger candidate against John McCain in the fall." Watch more of Clinton's speech »
It was not immediately clear which polls and states Clinton was specifically referencing.
Recent polls out of the crucial swing states of Ohio, Pennsylvania and Florida have indicated she has a better chance of beating McCain in those places than Obama. But Obama performs better in several other swing states that Democrats have historically had difficulty winning, such as New Mexico, Nevada and Colorado.
In a CNN general election national poll of polls out Wednesday, both Obama and Clinton lead McCain by two points: 46 percent to 44 percent.
The last general election poll of polls -- released May 15 -- showed Obama leading McCain by five points (48 percent to 43 percent) and Clinton leading McCain by four points (48 percent to 44 percent).
The national general election poll of polls consists of three surveys: Gallup (May 22-25/27), Newsweek (May 21-22) and Reuters/Zogby (May 15-18). The poll of polls does not have a sampling error.
According to the latest CNN delegate estimates, Obama has 1,978 total delegates to Clinton's 1,780.
But those numbers are about to change as Democrats head to the polls in three more contests, and depending on the outcome of a Democratic National Committee meeting this weekend.
The committee's Rules and Bylaws Committee meets Friday and Saturday in Washington to consider what to do with Florida and Michigan, which broke ranks to hold primaries earlier than party rules allowed.
As punishment, both state parties were told they would not be represented when the party officially nominates a presidential candidate at the August convention in Denver, Colorado, and they are challenging those sanctions.
The Democratic Party is likely to meet the states halfway when it comes to seating their delegates at the national convention, two members of the rules committee said Wednesday.
Such a move may help Clinton close the delegate gap with Obama but not overtake him, said sources familiar with party deliberations. Watch more on the Democrats' dilemma »
The sources did not want to be identified because the full committee has not yet discussed the problem or ruled on it.
CNN's Ed Hornick, Sasha Johnson, Alexander Marquardt, Alexander Mooney and Chris Welch contributed to this report.
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