ORLANDO, Fla. — Democrat Sen. Barack Obama used his appearance Tuesday at a Veterans of Foreign Wars convention to attack Republican Sen. John McCain's critique of him to the same group a day earlier, but he got a cooler reception than the Vietnam veteran did.

McCain, the presumptive Republican presidential nominee, continued to hammer away at his Democratic rival Tuesday, posing atop an oil rig in the Gulf of Mexico and charging that Obama doesn't have a realistic grasp of energy issues.

Meantime, Obama's newly minted running mate will join the Democratic hopeful onstage Saturday at a rally in Springfield, Ill., where Obama launched his White House bid, a campaign official said.

A senior Obama adviser told The Associated Press on condition of anonymity Tuesday that Obama and his choice for vice president will appear in front of the former state Capitol where Abraham Lincoln once served. The last time Obama appeared there, he announced he was running for president.

The disclosure narrowed the window Obama has to reveal his running mate. The list of possibilities is widely believed to have come down to Delaware Sen. Joe Biden, Kansas Gov. Kathleen Sebelius, Indiana Sen. Evan Bayh and Virginia Gov. Tim Kaine, who planned to campaign with Obama on Thursday in his home state.

Obama strategist Anita Dunn wouldn't respond directly when asked if the Springfield event would be Obama's first appearance with his choice, but she suggested the two wouldn't necessarily be related. The campaign has said it will announce the choice in a cell phone text message to supporters.

On Tuesday, Obama denied McCain's accusation that he favored failure in Iraq or that he was shifting his anti-war stance out of expediency or tailoring his foreign policy in an attempt to win the presidency. "Let's have a serious debate, and let's debate our disagreements on the merits of policy — not personal attacks," Obama said.

Obama said he wouldn't attack McCain's support for the Iraq war because "I believe that he genuinely wants to serve America's national interest" and that "now, it's time for him to acknowledge that I want to do the same. I will let no one question my love of this country." He also said that he knew there were Democrats and independents, as well as Republicans, in the audience.

While initially perceived as lower key in his response to recent Russian aggression against Georgia, Obama told the veterans Tuesday that, "I reiterate my demand that Russia abide by the cease-fire" and that "Russia must know that its actions will have consequences."

In Orlando, Obama drew applause for his pledge to expand health care coverage for veterans and for saying that he had "no greater priority" than routing al-Qaida and the Taliban in Afghanistan. He also said that McCain had been wrong to predict that U. S. troops would be greeted as liberators in Iraq and other strategic judgments.

"For all of his talk about following Osama bin Laden to the Gates of Hell, Senator McCain refused to join my call to take out bin Laden across the Afghan border. Instead, he spent years backing a dictator in Pakistan who failed to serve the interests of his own people," Obama said, a reference to former Pakistani President Pervez Musharraf, who resigned Monday.

McCain focused Tuesday on energy instead of international affairs or veteran's issues, which he addressed before VFW conventioneers on Monday. On a visit to an oil rig in the Gulf of Mexico, the Arizona Republican senator renewed his call for more offshore oil drilling.

"Senator Obama opposes new drilling," McCain said on a rig that he said sits atop 160 million barrels of oil. "He has said it will not 'solve our problem' and that 'it's not real.' He's wrong, and the American people know it."

Obama campaign officials dismissed McCain's blast as talk from someone who's been part of the energy problem.