HOPKINS, Minn. — Creating a potential headache for his campaign, Republican presidential candidate Mitt Romney said big businesses in the U.S. were “doing fine,” in part because they get advantages from offshore tax havens.

His comments echoed similar assertions about the state of big business by President Barack Obama which Romney has criticized. They’re also a reminder that the GOP candidate has kept some of his personal fortune in low tax foreign accounts.

“Big business is doing fine in many places,” Romney said during a campaign fundraiser Thursday. “They get the loans they need, they can deal with all the regulation. They know how to find ways to get through the tax code, save money by putting various things in the places where there are low tax havens around the world for their businesses.”

Romney’s assertions resembled Obama’s declaration earlier this summer that the “private sector is doing fine.” Romney and other Republicans pounced on the president’s comments and cast them as an indication that he was out of touch with the nation’s economic struggles.

Romney didn’t mention Thursday that he has kept some of his personal money in offshore tax havens, including accounts in Switzerland and the Cayman Islands.

The presumptive GOP nominee was to join up with his running mate, Paul Ryan, on Friday for a rally in Michigan. The duo also planned to appear together Saturday in Ohio.

Romney was campaigning and fundraising as his party readied for him to officially become its nominee for president. Republican delegates to the Republican convention will begin the roll call vote to officially nominate Romney on Monday, which could allow him to accept the GOP nomination earlier in the week than has occurred at previous conventions.

Republican officials said the formal presidential nomination process would begin earlier in part because of concerns about supporters of Ron Paul, one of a number of Republicans who challenged Romney during the primary, could seek to disrupt the roll call. Officials were also discussing the impact of Tropical Storm Isaac on the convention.

Ahead of the four-day GOP gathering in Tampa, Fla., Romney has sought to refocus his campaign on the economy after a week dominated by comments Missouri Republican Senate candidate Todd Akin made about rape. Akin said in an interview that victims of “legitimate rape” can biologically avoid pregnancy, prompting Romney and other top Republicans to call on him to leave his race. Akin rejected those calls.

Romney made no mention of Akin or hot-button social issues Thursday. He rolled out an energy policy that his campaign says would create more than three million jobs and centered his fundraising remarks on the economy.

Romney’s campaign sought to mitigate any potential distractions from his comments on big business and tax havens. Spokeswoman Andrea Saul said Romney “has long said we need to simplify the tax code, close loopholes and create a more level playing field for American businesses.”

In his remarks, Romney drew a distinction between big business and small businesses. He said that, if elected, he would seek to make it easier for small businesses to succeed.

The extent of Romney’s offshore investments is unclear because the presumptive GOP presidential nominee has only released his 2010 personal tax returns.

Romney’s campaign says he plans to release his 2011 returns later this year when the documents are ready. Romney has said he paid at least 13 percent of his income in taxes over the past 10 years.

Obama and his surrogates say Romney has a responsibility to give the public a fuller picture of his finances. They often cite the dozen years of tax returns Romney’s father, George Romney, released during his presidential campaign as a standard for candidates.

Many Republicans have also called on Romney to be more forthcoming about his personal wealth and income.

Meantime, Romney wrote an op-ed in The Wall Street Journal touting “what I learned at Bain Capital.”

“The lessons I learned over my 15 years at Bain Capital were valuable in helping me turn around the 2002 Winter Olympics in Salt Lake City,” he said in the article published Friday. “They also helped me as governor of Massachusetts to turn a budget deficit into a surplus and reduce our unemployment to 4.7 percent. The lessons from that time would help me as president to fix our economy, create jobs and get things done in Washington.”

As Romney pushed toward his party’s convention, Democrats unveiled more plans for their convention, which follows the GOP events.

Democratic Party officials announced a new slate of speakers, including two prominent businessmen: CarMax co-founder and former CEO Austin Ligon and Costco co-founder and former CEO Jim Sinegal.

Newark Mayor Cory Booker will also speak at the convention, a sign that tensions have eased between him and the Obama campaign after he criticized the president’s attacks on Romney’s private sector background.

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Associated Press writer Kasie Hunt in Washington contributed to this report.

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