Republican Mitt Romney dragged delicate US-China ties into explosive campaign politics Thursday, branding President Barack Obama a "supplicant" to a "prosperous tyranny" eyeing Asian hegemony.

The attack by the Republican presidential hopeful came as Obama's administration offers a tough love welcome to China's presumed new leader Xi Jinping, at a critical moment in the power politics of both nations.

"The sum total of my approach will ensure that this is an American, not a Chinese century," Romney wrote in an op-ed article in The Wall Street Journal.

"We should not fail to recognize that a China that is a prosperous tyranny will increasingly pose problems for us, its neighbors and the entire world," Romney wrote.

"We must... make (China's) path to regional hegemony far more costly than the alternative path of becoming a responsible partner in the international system," he said, apparently auguring a new tougher stand if he is elected in November.

Romney also described Obama's elaborate meetings in the Oval Office this week with Xi as "empty pomp and ceremony."

He also accused Obama of entering office "as a near supplicant to Beijing, almost begging it to continue buying American debt."

And the former Massachusetts governor again vowed to brand China a currency manipulator on his first day in the White House and to reverse what he said was Washington's current "trade surrender" to Beijing.

Beijing bashing is not unusual for major presidential candidates, especially in an environment in which many heartland voters in economically bereft industrial swing states complain that their jobs have fled to low-wage China.

Romney is currently locked in an unexpectedly tough fight for the Republican nomination, and faces a stiff challenge from his main rival Rick Santorum in a primary in one of those midwestern rust belt states, Michigan.

But candidates who become president typically moderate their rhetoric and fall into line with a four-decades-long geopolitical effort by US officials to downplay confrontation and manage China's economic and diplomatic rise.

The Obama campaign hit back hard at Romney, effectively accusing him of hypocrisy on Beijing policy.

"Mitt Romney will say and stand for anything to get elected," Obama campaign spokesman Ben LaBolt said in a statement.

"A commander-in-chief only gets one chance to get it right. That's problematic for Mitt Romney, who wants to have it both ways on the key economic and foreign policy challenges facing America today."

"Today's tough talk on China stands in stark opposition to his position two years ago, when Romney called the president's decision to enforce trade laws against China 'bad for the nation and our workers.'"

Romney criticized Obama's decision in 2010 to impose tire tariffs on Chinese imports as "good politics" but bad for America, saying that "protectionism stifles productivity."

LaBolt also accused the financial advisors who control multi-millionaire Romney's investments in blind trusts of pulling $1.5 million in investments out of China at about the same time the candidate decided to get tough on Beijing.

The Republican's attack appeared overtly political in several respects.

First, Obama specifically warned Xi in front of reporters on Tuesday that China must play by the "rules" of the global economy -- though Republicans will argue the president is doing little to back up his words.

Obama's Asia policy is seen by many analysts on both sides of the political fence as one of his more successful ventures abroad, and in an East Asia summit in Indonesia in November he outmaneuvered Beijing to bring up South China Sea territorial disputes.

It is also unclear whether US allies are, as Romney argued in his Journal article, questioning US staying power in East Asia.

Obama recently announced a new US Marine base in Australia and vowed defense cuts will not impact America's posture in the region.

In addition, much of the administration's recent policy in Asia appears to have been specifically designed to take advantage of disquiet in the region among US allies about China's rise, and a desire for a deepened American role.