CNN

Mitt Romney made the rounds at the Pepsi Center in Denver Tuesday.

DENVER, Colorado (CNN) - Former Presidential Candidate Mitt Romney came to the Denver on Tuesday to criticize Sen Barack Obama’s readiness to be president.

Watch: Obama not ready, GOP says

But the Massachusetts Republican spent more time at a press conference defending his own differences with the party's presidential nominee, Sen. John McCain, who aides say is strongly considering Romney as his running mate.

“On the major issues that America faces we agree,” said Romney about McCain. “We agree that you don't grow an economy by raising taxes. We agree that you don't grow an economy by cutting off trade. We agree that you don't grow an economy by saying we're not going to drill of additional oil.”

During the Republican primary season, McCain and Romney largely criticized each other over immigration reform and prior positions each candidate had taken on taxes, the Iraq war, abortion and gay rights.

“If you go back and look at debates held... you'll find each of us describing our differences with one another, and surely you'll find where one or another of us disagreed with Sen. McCain on one issue or another,” said Romney. “But you're never going to find someone saying John McCain wasn't qualified to be president of the United States.”

Romney also called Obama “a charming and fine person with a lovely family,” but said he is too inexperienced to be president - a constant message of McCain's campaign.

“His experience has not provided for him the kind of judgment, gravitas that is necessary to face the kind of challenges of world at large," Romney said.

Romney also took shots at Obama's newly-minted vice presidential candidate, Joe Biden.

"I think he brings experience, but if you look at Joe Biden's record with some 30 years in foreign policy experience, there's about 30 years of generally being wrong on foreign policy issues," he said.

The McCain campaign has signaled that they will likely announce the choice for the Republican vice presidential candidate later this week.