BOSTON (AP) -- Republican U.S. Sen. Scott Brown and Democratic rival Elizabeth Warren are embarking on separate tours of Massachusetts as they try to strengthen their appeal among business owners and workers.

The tours come as Brown steps up criticism of Warren, portraying the Harvard Law School professor as anti-free enterprise and saying she wants to "make America more like China."

"Warren ... is holding up China, with its repressive government policies, as the model for American progress," Brown said in a recent fundraising letter. "Being more like China is no way to strengthen America."

Brown pointed to a recent Warren television ad in which she says the U.S. spends 2.4 percent of its gross domestic product on infrastructure projects like fixing roads, bridges and schools, compared to competitors like China, which spends 9 percent.

Warren said the ad is meant as a warning that the U.S. needs to do more to help businesses grow. She said China is making the kind of infrastructure investments -- from water and sewer lines to power and communications systems -- that will give Chinese businesses a leg up over business in the United States.

"We can do anything if we can compete on a level playing field," Warren said in a statement. "But if China is making investments in state-of-the-art infrastructure while the United States lets roads and bridges crumble ... then our businesses can't compete."

Brown also criticized Warren's infrastructure plan, which she says is designed to help jump start the economy and create jobs. He described it as a massive new stimulus program, and said, "We've tried a big stimulus already and it failed. All it got us was more debt and fewer jobs."

But Warren said her program carries a $100 billion price tag, would pay for itself, and would not add to the deficit. She said one reason businesses are struggling is because of the billions given away by Washington in "special deals for big oil, Wall Street and billionaires."

"Now middle class families and small business owners are paying the price," Warren said in a statement. "We can do better. We can build a strong economy that works for everyone -- not one that's rigged for the big guys."

Warren said her plan would improve surface and air transportation networks, fix schools, make wireless broadband more widely available, give states more flexibility to use highway funds for mass transit projects and reinstate tax breaks for commuters. She also called for the creation of a national infrastructure bank designed to entice private investors into road and rail projects.

Brown also has tried to cast Warren as anti-business, highlighting a web video of a Warren campaign event last year during which Warren said "there is nobody in this country who got rich on his own."

But in the full quote, Warren praises business owners who "built a factory and it turned into something terrific" and said businesses also benefit from taxpayer-funded roads and bridges and other public infrastructure projects.

In an editorial on Politico this week, Brown called that "a phony argument" saying business owners also pay for those infrastructure projects.

"If only leftists like Warren and all Occupy protesters weren't so wrapped up in taxing and regulating them without end or in denigrating their achievements, these men and women would do even greater things and hire even more workers," Brown wrote.

The two candidates are planning to pitch their messages directly to voters.

Warren on Tuesday launched what she's calling a "Rebuild Now" tour highlighting her infrastructure and jobs plan. She said she will meet with workers and small business owners across the state throughout August.

Brown kicked off his own "Thank You For Building This" series.

Brown said he plans to visit a different small business in Massachusetts each week and deliver a gift basket of bagels and coffee to employers and employees in appreciation of their hard work.