Republican US presidential frontrunner Mitt Romney took heat Wednesday over his fierce criticisms of China from a Chinese-American woman who bluntly told him "it just doesn't make me feel good."

The woman, sitting near the stage at a political rally held by the former Massachusetts governor and veteran Republican Senator John McCain, repeatedly said she loved the United States and asked Romney not to put Asians down.

"I heard all this degrading thing about China this and China that, it just doesn't make me feel good," she scolded the candidate.

"I hope I haven't put any Asians down," Romney, who in his campaign speech routinely accuses Beijing of cheating on global trade rules and vows to "clamp down" on China, said somewhat stiffly.

"I admire China's economic success, it's literally a miracle," added McCain.

But "when you take people who are using the Internet and throw them in jail, when you imprison Nobel prize winners, when you repress the ability of people to elect their own leadership, when you carry out a basically totalitarian form of government, then I can't admire that," he added.

The woman, who did not give her name, also took aim at the Republican belief in "trickle-down" economics, the notion that cutting taxes on the wealthy benefits everyone by boosting investments that fuel job growth.

"It didn't help me. My tin can is still empty," she said, to scattered applause and cheers.

Romney fired back: "Let me ask you a question: Can you tell me where it's better to live, where the income per person is better than America?"

"Ours may be far from perfect -- and it is -- but it's just a lot better than anything else that the world has ever seen," he said.